Additional Selection Tool
The current selection tool is excellent for re-using areas of a drawing, often eliminating the need to draw objects repeatedly across many frames. I would not like to see the way this tool works changed, as it is great for many tasks.
However - an additional selection function, whereby the selected area would remain selected (marked by a dotted outline) would be VERY useful. So that one could select an area that could then be cut, copied, filled or cleared and this area would remain selected even when a different frame was selected. This would allow one to work on a specific area across many frames. An invaluable feature in hand drawn animation. The selected area would only be de-selected when a dedicated deselect button was clicked.
The selection tool is a little bit like the lasso tool, but instead of having to trace where you want to select, you can just tap. Using the selection tool, you can draw in specific areas that you might want to color. For example; you could use the selection tool in an outline of a character, go into a different layer, and color it in without coloring the background or other things you might not want to color in. There are similar tools like this in other drawing apps.