You need to manually create the configuration files under /usr/share/nemo/actions/
Im assuming application 'gmrun' and mousepad both are installed.
sudo apt install gmrun mousepad
Save the following as - open-gmrun-as-root.nemo_action (The extension part .nemo_action is trival).
[Nemo Action]
Active=true
Name=Run Program as Root
Comment=Run Program as Root
Exec=gksu gmrun
Icon-Name=nemo
Selection=none
Extensions=any
EscapeSpaces=true
Exit Nemo and re-open it. You will see the newly created Context menu there.
Following are the others configs I have-
=> edit-with-mousepad.nemo_action
[Nemo Action]
Active=true
Name=Edit with Mousepad
Comment=Edit with Mousepads
Exec=mousepad %F
Icon-Name=mousepad
Selection=s
Extensions=nodirs
EscapeSpaces=true
=> open-gmrun.nemo_action
[Nemo Action]
Active=true
Name=Run Program
Comment=Run Program
Exec=gmrun
Icon-Name=nemo
Selection=none
Extensions=any
EscapeSpaces=true
Following are the screen-shots for your information:
