many thanks. Yes, I knew that a long time ago. But mixed it up with the registered file type, where I entered json. (which obviously didn't help)
Just for other users: in most recent pspad, you find it at settings highliter settings <choose language> set extensions in File Masks another thanks, Klaus -- <https://forum.pspad.com/read.php?2,73145,73147> PSPad freeware editor https://www.pspad.com
