Allow disabling of the integrated text edit + use external apps to edit

### Is your feature request related to a problem? Please describe.
I am unable to utilise my default and superior modifier of text when I want to modify files that contain text.

### Describe the solution you'd like.
I want to be able to disable what Nextcloud includes as unnecessary duplication of this ability.

### Describe alternatives you've considered.
Zero exist that are practical and consequently relavant to this discussion: I am able to install PostmarketOS, but that solution benefits solely me, so it appears to be unfair.

### Additional context.
The custom modifier is slow and does not include basic ability: it is unable to search, automatically replace, is not extensible, and is solely possible to utilise within Nextcloud. I am unable to ascertain why it exists.