Having just had a forest battle, I found it was often quite tricky to see what areas were accessable and what areas weren’t (aside from hovering over each hex).
One really helpful feature (which appears, in a way, in the game Invisible Inc) is to have a toggled display that shows a clear display of whether hexes are accessable. This could either be done as a colour coded overlay, or a simplified/graphical display of the hexes that replaces the normal display (kind of like in Civ5?, where you can see a simplified iconic version of the map).
Maybe clear the trees, and show a colour coded hex overlay, when pressing a hotkey.
Would give a very useful overview of the paths available.