How to add/edit a DDF on Home assistant using text editor?

Of course I edited the original file before in the DDF editor. This way I can double test addon restarts. Expected outcome:

  1. Original file will be overwritten, content set back to default
  2. Custom file will still exist and stay untouched (persistent)

Surviving an dddon restart would already be very good. Addon update is a manual process (no HA addon auto updates) and making that change (maybe by a one-liner CLI command) again after every update would only be one additional step on my update check list.