Problem: I want to sync data from a Linux PC to a NAS Samba share. You do impose a constraint that a GUI should be available. I’ll bear that in mind.
If you can access it via scp (which is very likely, but you don’t mention the NAS model) then use rsync or similar - multiple GUIs are available and it sounds like you’ve found some already
It’s a Samba share, mount it and then sync data. GUIs are available for the sync bit. Depending on your distro a GUI may be available for the mounting thing. If you specify a mount in /etc/fstab then it is a permanent mount.
I suggest you break the problem down into two bits and solve those independently. The first one is data access ie via Samba and the second is the sync bit.