I see this documented around the interwebs quite a bit and always with the same limitation of only working correctly with files that contain no spaces in the filename. This is an easy fix so I’ll go over it all again below.
Create a new file in /usr/share/nemo/actions (you must maintain the .nemo_action file ending). Let’s create a new file called shred.nemo_action with the following contents:
Comment=Securely Delete File
Exec=shred –force –remove –verbose –zero %F
The key part that most people miss is the “Quote=double” option. This is what allows the action to run successfully on files with spaces in the filename.