Most of the time doing something like this i’d SSH in using something like PuTTY and edit my files using the command line. If i wanted to copy files on and off the Pi then i’d copy them first to /home/osmc and then move them into the correct position from the command line.
From PC to Pi
Copy to /home/osmc using something like WinSCP
Move to correct location using SSH client like PuTTY
From Pi to PC
Copy from elsewhere on the Pi to /home/osmc using SSH client like PuTTY
Move to PC using somethinfg like WinSCP
You could alternatively enable the root account and log in to WinSCP using using that to gain full access to the filesystem or i think edit your shell preferences to do the same thing with the osmc account (Dilligaf explains how to do this here WinSCP Permission Denied - #3 by Dilligaf) but i myself wouldn’t bother and would do it manually.
These don’t help you if you wnated to do this via Samba but you probably don’t need ot do it via Samba.