Unfortunately it doesn’t help you with your current data loss, but there is now at least a partial safety measure taken for this situation in the upcoming v8.9.3 - for the case of a modified file, that Reload-dialog offered default answer has been changed from YES to NO:

npp-safer-reload-default-for-dirty-files.png

For unmodified files, the default remains YES.

March 2026, by the fact there is still no smart highlighting over lines, would fully indicate there is no intention to add such a feature.

I tried the Mark All method, worked nicely. However, one important note, one needs to make sure exact words in the find box is turned off, any non-alphanumericals, including space, and definitely EOL chars, will cause a non-match.

Only downside is doing this for all custom languages (i.e. 10 in my case) effectively duplicates them and makes the Language menu quite cluttered and hard to use.

It would be nice, if UDLs would be sorted within the preinstalled languages, but as far as I remember this wouldn’t be trivial to implement…