What determines where auto support is placed?
It seems to be placed in the front of the model which typically needs subsequent careful removal…
instead of placing such support at the back??
The software adds it to the place it thinks is best.
And how should the software know what’s the front or back of your object? 
I will try a 180 rotate and see what happens…
may be its back to the future
Why do you think that would make a change?
The supports are there to avoid things falling down as the printer can’t print into thin air. So they are placed under overhanging parts.
Maybe you should share your file
The supports are placed based on how steep the surface is. Vertical surfaces don’t need supports, but increasingly leaned over surfaces will need it at some point. Luban lets you adjust what angle is considered too steep, and the option to only place supports on the build plate or allow it to build supports on top of the model too. Without seeing your model, there’s 2 reasons I can think of. Either the front of the piece is steeper than the back of the piece. Or the back is above something and you have supports only on the build plate.
I’ve found the layer height changes the overhang I can print reliably. At 0.2mm layer height, I can only print 50º before I need support, but 0.1mm can print 60º without support. But there are a lot of variables here, like enclosure, model size, the room temperature, and cooling time.
Ok, awkward looking object. Any reason you’re not printing it laying down? (maybe it’s a litophane?)
As mentioned already by some others, experiment with changing the overhang angle.
When printing an object like that, make sure you don’t have sudden movements in the Y-direction or it might just fall over (think infill that might make jerky movements, if you 100% infill it’s probably OK as I would expect that it’s filling in the X-direction and not Y-direction). And you might want to use a raft to make sure it’s stuck to the bed pretty good. (can’t really see if you have one.)
You can have a horizontal offset on that, to keep the branches away from the part except where absolutely necessary.
under Expert or allsettings
Support x/y distance
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lovely jubbly…
'cept I cant find Luban expert or all settings options 
must be getting punch drunk …
or are these settings cura only?
TIA
yeah thats cura only… i thought you were using cura because that looked like trees because i am barely aware of my environment anymore. sorry.
Just to say that after a bit of trial and error using Lubans rotate option, Ive found that there seems to be a sweet spot that avoids trees being generated.
I dont know if its generally true but at least it avoids my problem with branches
I find that trying to trick the slicer into avoiding supports just causes other problems. I mean, you can just disable supports. But then you’ll probably end up with some spaghetti filament to show you why it was trying to generate those supports.
Cura has a new feature called Tree Supports. Instead of building supports vertically like scaffolding, it builds them off to the side. They really do like like a tree growing out of the build plate, that leans over to support the print. They can be a bit slower, but I’ve been much happier with the quality of the print. Cura is pretty easy to pick up from Luban, since Luban uses the CuraSlicer library behind the scenes. The only downside it’s that it’s 3D printing only. There’s even plugins to add all the Snapmaker functionality, like printing over wifi.
