A couple months back, I picked up the use of Show Comment Indicator (in Tree Display setting) to display which components have a comment, from a discussion here on the forums. I use it to identify anything defined temporarily (so I can remove it when the proper conditions are determined), or if something carries a driving distance mate to which many other components' position is dependent. I used to accomplish this by renaming mates to include keywords like DRIVING or TEMP, which I could later search for by name and remove or alter, as needed. The Comment Indicator is a visual key which I can find easily enough if I'm looking in the applicable portion of my design tree.
I really love it. I could love it more. Let us color-code the Indicator.
I can imagine using more comments to the point where there's no longer just one commented part in a subfolder, so that one placed as a marker no longer stands out as unique. It could be used to carry various status or intentions as needed, such as progress, workers assigned, placeholder, or whatever a user wants.
The Comment Indicator looks like a Square notepad with a bottom corner curled up. This visually resembles a trademarked office product which includes adhesive on each sheet in a stack, produced by the folks at Trois Em, which does not need its name repeated in this thread. Those products famously come in a variety of colors. This idea just about suggests itself by associative reference. (The screen icon lacks adhesive, fortunately. Trademark by others does not apply if its name is not used.)
The choices and UI for this should be simple and limited yet customizable, just like the 'palette' UI for Line Color, and not like the comparatively very complex and option-rich Appearances FM.