LightBurn doesn’t have a corner fillet tool yet (it is being worked on though). In the meantime, here’s a trick to let you make radiused or chamfered corners on any shape:
Select your shape:
Click the Offset tool:
Offset Inward by the radius amount, and set it to delete the original and select the result:
Then, offset the result back outward by the same amount:
The result (Bevel on the left, Round on the right):
