This looks like a problem not only for “office files”, but a synchronization issue in general!
- Placing a file on the local nextcloud folder does not upload it to the server.
- Editing a file (as simple as a plaintext) does not saves the changes in the server
It should be clear that the “synchronize” action of the android app has a different meaning than the synchronization of desktop clients. In the android client app, the sync is one-directional, from the server to the client exclusively. Uploads (client->server) are only handed individually, on a file-per-file manner.
This is a very useful feature that is lacking. With double-sided sync’ing, one could for example edit simple plaintext seamlessly, or have configuration files (such as e.g. user dictionaries, book annotations, app config files, dotfiles, metadata files etc) synched seamlessly between devices. It is completely NOT FEASIBLE to always upload all config files one by one.
For reference, last time I checked, the dropbox android app was similar: folder changes were ignored, but editing a single file in android would sync it with the server. The defunct ubuntuone had no such functionality. This seems like a nontrivial task to implement.