Sorry for taking so long to get this out, but here’s a guide following how I did the non-planar engraving examples.
NOTE: This is not completely comprehensive, I’m sure there’s several ways to do this, including custom post-processors, custom tools etc. This is just the method I used and the examples within are very simple, more complex use cases can be done and may require tricks not outlined here.
First off, I’m not great at Fusion360 yet, my job doesn’t afford me too much time to just sit and learn it so bear that in mind for the simple objects here. Also note, this method works best with things designed in F360 and not imported mesh, specifically since you’ll want to select only certain faces and not the entire thing. If you import a mesh, you have to have F360 try to rebuild it and can become a mess with organic surfaces. Experts only going down that route, and since I’m no designer, it’s outside the scope of this guide. 
Materials and Machinery in this guide:
Snapmaker A350 + Enclosure + 10W Laser Module (1.6W works as well)
Model to be machined: Little swoopy thing I made in fusion. 
Software: Fusion360 + Text Editor (such as Notepad++)
Guide Links:
I: Preparation
1: Measuring the depth you can laser.
1a: Since the laser modules have the black shroud and a fairly close focal point, the shroud hitting your workpiece becomes a potential issue if you’re lasering too steep of a surface.
1a: The easiest I found is simply make an object in luban, set the laser power to 1% and set the speed to slow (just so it doesn’t whip through, these values don’t matter much). Load to workspace and start it with a material height of say, 0.01mm. Pause the job and measure the distance between the shroud and the laser bed.
1b: The 10W laser appears to have 20mm to the shroud, so you may just be able to use your focal length. Mine is 29mm, and my measured distance was 9mm. The 1.6W you WILL have to unscrew the end of the shroud, since it’s normally 2-3mm above the workpiece. However, this gives you more room than the 10W and the shroud is smaller, so less chance of bumping.
2: Only use 50-60% of the resulting depth to ensure clearance for the laser shroud, unless it’s a long gradient.
2a: This image from hack-a-day (although for non-planar 3d printing) shows this better, think of the 10W as an E3D nozzle, and the 1.6W as a Merlin nozzle. (long focus chinese lasers have absolutely no problem with this, since they focus so far away, they just lack much in Z movement so that’s going to be your limitation)
II: Make A Test Model
1: While I won’t go over design in F360, I will suggest making a test model first, something with some gentle curves, swoops, etc.
1a: This little swoopy thing is what I came up with:
It’s 5mm at the top, and 1mm in the valley, so with a difference of 4mm, even at the valley, my laser shroud will be 5mm above the top.
2: Either mill or (if you’re lazy like me) 3d print your test model. KEEP IN MIND THE POTENTIAL HAZARDS WHEN LASERING PLASTICS AND ENSURE GOOD VENTILATION
III: Setting Up Laser Path
1: If you 3d printed your model, make sure to bring it into the manufacturing section. If you milled it, you’re already there!
2: We’ll be setting up a finish pass with only ONE pass across the top since we’re engraving and we want it at the finish depth.
3: Set up a repeatable origin at the lower left.
3a: If you plan to 3d print, then laser an object set the origin at the bottom of the model
3b: If you mill the object, then laser it make sure you have a repeatable origin point, either the top or bottom You can check my CNC repeatable origin guide linked above, specifically section V. Then you can use the CNC/Laser platforms as your repeatable origin.
3c: Follow both origin guides above to ensure you can line up with the corner origin after swapping from CNC to Laser.
4: With the origin chosen, if you do not already, make a tool with a fine tip (I used my 10 degree engraving bit setup with a 0.1mm tip).
5: Assign the tool with a finishing pass to the curves/surfaces/etc you want laser engraved. You can use any of the finishing processes you want, such as parallel or morphed spiral (which I recommend to make continuous, vs potential burning at edges on direction change).
5a: Setting up the pass, use the feedrate you want to laser engrave at, since I’m using the 10W, I set this at 3000.
5b: In the geometry tab, I used silhouette and tool center on boundary, this of course will depend on your project, model, etc.
5c: In the passes tab, set the stepover to match your laser kerf, i.e. 0.1 for the 10W, 0.2 for the 1.6W, select both ways for direction and up/down milling.
6: Review your preview to get an idea of what it will be doing.
(note my origin is the TOP of the bottom left, I did this since I could just set my laser down on the top of the model for the origin since I 3d printed the object)
IV: Modifying The GCode
1: After you’ve verified your paths, post-process as you normally would (if anyone needs, I can link my CNC guide for this).
2: Rename the resulting *.cnc file to change the file extension to *.nc so the snapmaker knows this is a laser file.
3: Open the .nc file in a text editor, there’s many changes here, but they’re rather simple and for safety.
3a: At the very top of the file, remove these two lines, they turn the spindle on and wait for the spindle to reach speed, you don’t need the laser coming on here.
M3 P100
G4 S2
3b: Near the top, turn on the laser at the proper place. You’ll notice it starts at a safe distance (default 15mm) You’ll want to put an M3 with your power setting on the line after it reaches the actual machining height. This is between the lines where X/Y actually change.
G1 X50.310 Y-0.008 Z15.000 F3000
G1 X50.310 Y-0.008 Z-0.500 F3000
G1 X50.310 Y-0.008 Z-2.183 F3000
M3 P25 S63.75 (This is 25% power, full power would be P100 S255, the PX shouldn’t be necessary though)
M3
G1 X50.303 Y-0.008 Z-2.252 F3000
3c: Search the document for each retract to turn the laser off to prevent burns, and to turn the laser on only when in position. The CNC will lift up (by default 5mm, so search for Z5.0) for fast travel moves, while using the CNC it isn’t a problem to leave the spindle on, for the laser, it’s important to turn it off. Use the find button in your text editor. You’ll want to turn off the laser (M5) before the retract line (Z5.0) then back on using the same info as above.
G1 X98.855 Y82.407 Z-1.476 F3000
M5
G1 X98.855 Y82.407 Z5.000 F3000
G1 X61.586 Y64.009 Z5.000 F3000
G1 X61.586 Y64.009 Z0.004 F3000
G1 X61.586 Y64.009 Z-1.780 F3000
M3 P25 S63.75
G1 X61.579 Y64.009 Z-1.848 F3000
3d: At the very end of the file, move the last M5 up to before it makes the last retract move.
G1 X-0.444 Y49.990 Z-2.169 F3000
M5
G1 X-0.444 Y49.990 Z15.000 F3000
G0 X0.000 Y0.000
V: Run Your Project
1: I would suggest transferring the file to the snapmaker via wifi or USB and running it locally to ensure proper origin alignment.
2: If everything goes well, you should get a result similar to this;
Your laser should follow the contours and keep the proper focus height throughout your project, if there’s multiple sections, the laser should turn off, move 5mm up for safety, move to the new position, come down, and turn the laser back on to continue.
VI: Afterthoughts
1: Some potential use cases come to mind, such as filling in engraved text, mocking up a real world object (such as a flask) to ensure laser focus across the curved surface, or just adding patterns.
2: You can also increase the stepover to do designs, such as doing parallel with a 0.5mm stepover, and a 2nd pass at 90 degrees to get a neat crosshatch. Use a wider stepover with the morphed spiral to get a neat effect following the outside contours similar to cocentric infill.
3: Get creative! If you decide to use this, post any results here. I’d love to see even just some test pieces, fails, what have you.
4: Feel free to drop any questions/comments and I, or other users, will try to answer them.
Bonus: While I reused a lot of images from my original post about it, I figured I’d put them here as well. My attempt at an organic engrave, it was a pain to select the proper areas, but that’s just my lack of experience.
Again, props to Eastman for the model, that I butchered and squished for an engrave.
