[Feature Request] Persistent clipboard between mounted directories in the file manager

[iamnadaman]

I tend to transfer files back and fourth between my NAS, so I think this feature would be quite handy if it's possible, and would be another option for this use case (the original being https://github.com/cy33hc/switch-ezremote-client)

This could also be useful if someone wanted to transfer files from USB storage to the microSD card locally.