Q: PCmanFM - How can I remove an entry from the context menu? I am using Lubuntu 18.04. 
When clicking right on a file the context menu of the file manager opens up. The file manager is PCmanFM, a great tool. I would like to remove programs from the list of suggested programs to open a certain file with. 
For example a text file can be opened with Leafpad and with AbiWord in the default installation of Lubuntu 18, already.
I understand that the entries result from several ways of adding them. Adding such an entry seems to be easier then removing one. 
Is there a documentation of the several ways on how to remove entries in context menu of PCmanFM?

A: There are different ways in which that list is created. Some applications ar associated by default (or they associate themselves when installed) to a certain file type or to folders. In this case they are listed in that file's or folder's mime-type line in /usr/share/applications/mimeinfo.cache or ~/.local/share/applications/mimeinfo.cache.
After selecting the "Open with" option in order to use a new application, that is then added in the same way to ~/.config/mimeapps.list.



*

*In order to completely remove an application from the list, remove it from the  line corresponding to a specific mime-type in /usr/share/applications/mimeinfo.cache or ~/.local/share/applications/mimeinfo.cache or  ~/.config/mimeapps.list.

*In order to downgrade the application in the list (keep it but put a different one on top of the list), use again 'Open with' to select a new application or command — even using a command line option, as said here.
In this way one can also fix temporarily the Firefox bug of opening downloads folder with a media player or other unsuitable program.
