I've paid for it and I compiled it in.
It just isn't supported in the bytejam setup, because... it basically sends changes to a file that is on disk, which is updated by tic80, and then sent over after that is updated.
(If I understand what it does from how it works, without looking at the code, because don't have the server side code. And I only looked at the client side code long enough to say "nope not changing this now")
I prefer the external editor and will continue to complain about this until I fix the client and server or someone else does (read: I fix it)