That could work. Perhaps it could build on the existing "manual download" mode for attachments (which may not work in the Rich Text Editor).
Comments:
- Attachments can be associated with multiple notes. For example, if a user locks an existing note that shares resources with other notes, the note encryption feature should be able to handle this. (See comment).
- Because of sync, it can be difficult to tell whether an attachment is associated with multiple notes.
- One solution might be to duplicate/copy resources when locking an existing note. However, this approach could result in a large number of duplicate attachments (and would keep a copy of the original attachments, unencrypted). For reference, there's existing logic for ensuring that each attachment is associated with at most one server share by duplicating attachments.
- The proposal suggests adding new syncable database properties to
notes,folders, etc. This could cause compatibility issues with older Joplin clients during sync if these properties are discarded. (See @mrjo118's comment in a similar thread, sync serialization logic).