SUMMARY How about having indicators (eg: a tiny triangle centered at the clips' edges) for the start and end of clips located at the timeline? It would be great for quickly realizing the clip's "fragment" being used in the timeline has "no more room" for creating a mix (same-track composition/transition) or for increasing its length. As soon as the clip's fragment has at least 1 frame of room, the correspondent (start/end) indicator disappears, and as soon as a resize happens reaching the clip's end/start the proper indicator reappears again.