It sounds like you are using multi-segment lines. If you use single-segment lines you can delete single lines without deleting entire sections (see tips below). In any case, an Eraser for the drawings in Roll20 is a very difficult prospect since Roll20 uses Vector and not Raster for the drawings. Here are some tips for drawing your dynamic lighting barriers: 1) Do not use freehand because it can slow down a computer. Use Polygon/line or square/rectangle instead. 2) Do not use Circles/Ovals, they will not work like you would expect. Instead, use polygon/line to create a curve (an exception to #3 below). If necessary, create a circle on the token layer and then trace it on the DL layer (cyan and yellow work well for this). I suggest 1/4 or 1/2 circles rather than a full circle (due to #3 below). For tiny circles draw larger circle pieces and then as a group shrink the circle. 3) Use single line segments whenever possible. If you make bends in your lines it can make it difficult to select, adjust, or otherwise correct your Dynamic Lighting barriers. 4) Hold the shift key to draw straight lines, then move the line where you want and adjust it's size as necessary. 5) Alt+arrow keys work wonders for minute placement adjustments. 6) When you put in lines that you intended to remove later (such as doors) make them a different color for easier identification. 7) Finally, as a personal preference, I like to recess the barriers slightly from the walls, doors, etc. so that players can actually see the wall rather than a black barrier.
