Help creating legends

With complicated diagrams, I often need to create a legend explaining the meaning of different note symbols, colors, lines, notes with outlines, etc. I don't see an easy way to do this.

I can picture two ways to speed this up.

1. A tool to "create legend textbox" that includes all the symbols and colors in use. I could then edit the descriptions, and delete the entries that aren't important. Colors could be shown both as rectangular color blocks (to show systematic color choices) and as individual colored symbols (to show specifically what a red triangle means). Again, I could keep the ones I want, and delete the ones that are unnecessary.

2. A symbol panel that lets us copy/paste individual symbols available within the program or (ideally) the ones actually used in the diagram. The panel could also include a list of all the colors currently used in the diagram. That would be a big help. I often wind up with a few shades of blue or green, by accident, intending them all to be the same. (Color management is a bit hairy at the moment. It's hard to add custom colors without overwriting existing custom colors. When I select a different custom color slot, the current selected color gets overwritten. So I need to remember the RGB of the color I want. That's another topic. But a list of all colors in use would simplify things a lot.)