Well, the point of using the GUI to clear the file was to use as few terminal commands as possible. Touch is not necessary as it doesn't get deleted (unless you delete it manually) and cron was an alternative way, not to be used together with chattr of course.
Actually cron might be the best option I have found so far, as I just read that "recently-used.xbel.xxxxx" tmp files are made and then moved to "recently-used.xbel". What happens when it cannot be moved I don't know. Nothing? Hundreds of tmp files? Perhaps recently-used.xbel could be made as a folder or symlink pointing to /tmp or /dev/null or something ?
A way to disable this feature is needed.EDIT
So it seems the correct way to disable this is setting "gtk-recent-files-limit = 0"
in either .gtkrc, .gtkrc-2.0 or .config/gtk-3.0/settings.ini. Unfortunately this doesn't work in Cinnamon EDIT 2
Is this an academical discussion or am I missing something? Turning it off in the Cinnamon Settings removes it fine here