Hello, currently this functionality is not available and is not planned.
If you want shell access to the device if you are behind NAT (Private IP), maybe you could use reverse SSH?
For example:
(Command on TRB) Router connects to your SSH server and forwards port 2222 to port 22 (its own local shell):
ssh -R 2222:localhost:22 81.29.20.20
You may need to login on TRB using your SSH server credentials
On SSH server:
ssh localhost -p 2222
Login using TRB credentials
This will initiate a reverse SSH connection so even though TRB initiates the connection to server, shell is opened on SSH server.