I would like to toggle visibility of folder tracks, while keeping its content visible.
Folder tracks are great for organizing large templates, but they can take a considerable amount of vertical space, especially in multi-level hierarchy (folder in folder). Flattening tracks hierarchy would allow user to see only content tracks without folder tracks.
For example, to show a single track that is inside two folders deep hierarchy, Cubase will display three tracks (eg. Strings -> SM Solo -> Cello). Hiding folder tracks would display just one track (Cello) instead of three.
This is important because vertical space can be quite scarce when lower zone is visible.