Can I (or another web app) edit the files in the data directory?

I have a text file (an HLedger file) in the data directory that I often update with the text editor. At the same time, I would like to have another web app (HLedger-web) to serve and edit this file. Serving it readonly would be no problem, I guess, as long as I don’t move it, but will editing it be a problem?

It’s generally not advisable to directly edit files in the data folder as this causes a database inconsistency. A better solution is to use a separate folder on the server and then connect it in Nextcloud as external storage.