I think a nice feature, especially for new/exploring users, would be to visually mark "hotspots" - places, where one can click in order to execute some action.
I imagine such hotspot as semi-transparent circles, with left/middle/right side filled, if there is L-M-R mouse button action available.
For duplicated items (like tracks, tree elements etc), a hotspot would be displayed for just the first item.
All distinct hotspot places should be marked in this way. A separate marking (like a symbol in the circle) would be available, if writing characters with given element active execute some action (fe. search).
This feature would be aimed at learners/explorers/as a remainder, not to be permanently displayed at all times.