I don’t know if this happens on Mac or Windows.
While testing an issue someone else was having I removed my configuration directory to start with a clean config and after opening up LightBurn I tried to adjust the window size because it was giving huge space allocation to the right side Controls frame. When I pulled the frame handle to enlarge the drawing area, once I released the mouse button and movement of the mouse into the drawing area it resulted in the Control frame shifting back again. When I import an exported config instead of letting LightBurn find my device LightBurn wants to give the Control frame the whole window.
Once I exit LightBurn and it writes the preference file the frame size adjustments operate normally. ie it looks like an uninitialized state problem.