Ubuntu – How to remove duplicate element from context menu

Considering the example from the answer - of using the "Open with" option:

The command sudo chmod +x must run in a terminal (gnome-terminal -e "sudo chmod +x %f") or alternatively the line Terminal=true should be in a desktop file in ~/.local/share/applications/make_exec.desktop:

[Desktop Entry]
Name=Make file executable
Exec=sudo chmod +x %f 
Icon=path/to/icon
Terminal=true
Type=Application
StartupNotify=true
NoDisplay=true
MimeType=text/plain;

For an application to appear in the context menu, it may need a desktop file in /usr/share/applications, but also you may need to edit as administrator /usr/share/applications/mimeinfo.cache and in the line of the intended file type to add the application.desktop.

So, in the present case, open /usr/share/applications/mimeinfo.cache and add make_exec.desktop to the line text/plain.

Considering the creation of custom actions - like in Thunar, Nautilus or Dolphin:

PCManFM supports custom actions.

Those created with Nautilus configuration tool (for Nautilus) appear in PCManFM too. These are .desktop files created in ~/.local/share/file-manager/actions. So, they can be added manually without the Nautilus tool.

The form of these files should be like those presented here or here.

So, for the present purpose, create the file ~/.local/share/file-manager/actions/make_executable.desktop with these lines:

[Desktop Entry]
Name = Make executable
Tooltip = Make this file executable
Icon = terminal
Profiles = make_exec;

[X-Action-Profile make_exec]
Name = Make executable
MimeTypes = text/plain;
SelectionCount = 1
Schemes = file;
Exec = sudo chmod +x %f

You can fix the missing context menu. I suggest removing the installed PPA version and the ppa (How do I remove a PPA added via command-line?), reinstall the version from Ubuntu and follow the instructions I derived from the bug reported: https://bugs.launchpad.net/ubuntu/+source/rabbitvcs/+bug/1093533.

You need to download the following file http://rabbitvcs.googlecode.com/svn/trunk/clients/nautilus-3.0/RabbitVCS.py

Copy it (using root/su/sudo) to:

/usr/share/nautilus-python/extensions/RabbitVCS.py

You may also need to create the following symlink:

sudo ln -s /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0 /usr/lib/libpython2.7.so.1.0

You will need to restart your session (log out and back in again) to see the changes.