A global navigation, allowing quick access to search and other content; In larger screens don't use sidebars, as those hide content
A presentation mode. All kinds of content need to work in this mode, studies, as an example, can be converted to something like Marp or Remark
Bible following OSIS schema
Hymns, with automatic refrain repetition in presentation mode
A text editor, allowing editing current content. That's mostly to fix typos, but needs to also allow removing and adding new content. Edits are stored as unsigned patches. Loading edited content will show warnings until those patches are merged to content and signed.
A form to share those editions between devices, using P2P if possible. Digitally signing those changes is needed to prevent possible attacks
What is wanted:
following OSIS schema