To activate this, press the ` key. (left of the number 1)

It looks to be for experimental or debugging purposes as the HELP function reveals only three possible commands: echo, set and show.  Of course it is entirely possible that other commands do exist but aren’t documented in the HELP function.

A popup command line option in a news aggregator GUI is an interesting concept and can be useful for quickly adding feeds and folders or sending commands to change feed display settings.  I’d love to use something like this to set ad hoc filters.

If anyone knows what this is there for, I’d love to hear more about it.  If you’re hacking away at the shell and discover something cool, do share.