[Chen]

probably an unusual comment - MobileSheets is just too powerful sometimes

When setting the display mode for a piece, there is a prominent "apply" button, which then asks if the setting should be applied to the whole setlist, or all pieces in the library.
A similar far reaching setting is in the cropping dialog for a file: Crop: Current page only / All pages in selected file / All pages in all files.

Depending on how one organizes their library "All pages in all pieces" setting is outright dangerous, as a erroneous application seems not reversible without restoring the last backup.
My Mobilesheets library contains over 100 setlists,  4500 pieces in a few hundred PDF files, many of the pieces with individual display settings and most of the pages cropped manually at some point.
Applying a new universal crop/display mode to all my files will most likely never be the correct operation. I always have a slightly uneasy feeling when cropping some new pages, that i could inadvertently apply the crop to the entire library and destroy all the settings.

I do not suggest to take away a powerful feature, but maybe it can be protected by a library setting "Allow 'apply to ALL pages in ALL files': YES/no"?  So it can be disabled if the power can only do harm...?

Thanks,
  Christof