This nemo_action file will add an entry into the context menu (when you right click) to give you the option to copy the full path of the file you have selected.
This file should be placed in /home/username/.local/share/nemo/actions or /usr/share/nemo/actions.
If you use Arch or an Arch-derivative, you can also install from the AUR here.
Dependencies: diodon, xclip, node copy-paste
Acknowledgements: thank you to envie on this website for the information needed.