The Auto-open switch makes the tree automatically open selected items, so that all subfolders are visible, whenever you select one. This makes it easier to browse through structures containing many folders. The switch also makes the browser show all presets available in selected folder including all subfolders (except when you select the root folder).
The Open all button expands the whole tree, so you can see all of the folders. This may be handy when editing large preset structures.
It would be great if the same features were available in the Parameter Lists (in Parameter Modulation). Much less scrolling would be needed and it would be easier to find the parameter you want. For example, here is the list of parameter groups for MMultibandPhaser (as seen at present) and the suggested collapsed version with the 2 new buttons:
... Big pic: http://i.imgur.com/RZFg3JR.pngIt would be extremely valuable in MXXX where where have gazillions of parameters: 16 groups of LFO parameters, 16 groups of Multiparameter parameters then the bands with their FX. It would better if the LFO groups were in a new group ("16 LFOs") and the Multiparameter groups in another ("16 MultiParameters"). And possibly, those new groups placed after the Band 'branches'. As in the 2 mock-ups on the right-hand side:
... Big pic: http://i.imgur.com/PAxL7iQ.png
