Hello, please look also to the description and discussion in the forum: https://forum.xfce.org/viewtopic.php?id=9732 .................................. The xfce wiki says for thunar : "Working with Files and Folders - Modifying Actions (...) To remove a previously added action for a file type, bring up the Open With dialog as described above, right-click the action you want to remove and choose Remove Launcher." .................................. But this is still not possible, you have to change this with editing the files stored in $HOME/.local/share/applications ... deleting wrong selfcreated actions, saved as file in '$HOME/.local/share/applications' ... deleting wrong actions in the file "$HOME/.local/share/applications/mimeapps.list"... .................................. So we should change the description in the wiki... .................................. User hjudt means, this problem is caused of different glib-versions.
The wiki entry got fixed meanwhile. However "remove launcher" still is grayed out. Opened a thunar bug for that: Bug #14393