shift++ and shift+- work only with the numpad
...which is not that great if you have a smaller notebook without the numeric block.
Proposed:
either shortcuts that work equally well with the numpad or the main keyboard,
or auto-remapping them by pressing a button in Preferences > shortcuts.
System used: MuseScore 0.9.4, Polish Windows XP, all service packs/updates installed (maybe it is keyboard mapping related, as at least one of the shortcuts seem to work ok in version 0.9.3).
Comments
This is a known issue. As a workaround you can change the keyboard shortcuts in the preferences.
The German keyboard had the plus sign in a different place which means + and Shift++ are different and do not conflict (even on a laptop). However this is a problem for other keyboard layouts.