TL;DR : Press the prefix key twice
In this short blog post, we'll explore how to send tmux commands to a remote session while working within a local tmux session using the same prefix key.
That is, you have a local tmux session, you have connected to a remote host via ssh within this tmux session and now you have opened a new tmux session within that.
This scenario creates a "nested" tmux session. To send commands to the remote tmux session without changing the prefix key, you simply need to press the prefix key twice.
For example, if
Ctrl + b is your prefix key, then press and hold
Ctrl and then quickly press
That should be it