Nautilus and Thunar have a such context menu option under Properties/Permissions, but not PCManFM, Lubuntu's default file and desktop manager (at least not yet in the present v. 1.1.).
But under "Open with"/(again)"Open with"/"Custom command line", it is possible to add new custom commands.
This creates a file with extension
~/.local/share/applications which can be edited further so as to get a proper name and icon.
What is the command to add in this way for making a file executable?
That is: how to use
sudo chmod +x filename to make it work in this way?