When heating only the center of the bed, the primer line is still printed on the edge, which is not heated… so the filament does not stick on the ground print and mostly get stuck on the nozzle…
If you do not remove it manually right at the beginning, this piece of filament could just stay in the way of your print… not good !!
When heating partially the bed, the primer line should be printed on the edge of the heated area !
You could disable the purge line, set your skirt to a single layer, and use the skirt as your purge, which would guarantee it to be in the heated zone.
What slicer are you using? If it’s Luban, it seems you can’t edit the start/end gcode, so you’ll have to do it manually. Make sure your adhesion type is either skirt or brim, both will purge your nozzle fine. Brim will help with adhesion if you need it.
To remove the purge line, export the gcode to FILE then open the file in any text editor. You’ll need to remove the following lines;
This is the purge line, it moves down to Z0.5, resets the extruder (G92 E0), then runs 30mm of filament 150mm on X. Removing these five lines should remove the purge line entirely.