1. Do you need hotkeys to switch from one sub-application to another?
Riena has already define hotkeys to switch form one sub-application to next (ctrl+page up) or to previous (ctrl+page down) sub-application.
Also you can use mnemonics to active one sub-application. Add the character "&" inside the label of the sub-application.
ISubApplicationNode subApplication = new SubApplicationNode(new NavigationNodeId(
2. Do you need hotkeys that only work in the context of a special sub-application?
Riena doesn't support this. Because not special context is activated for sub-applications.
If you need this, please open a bug.