Need to be able to add custom user agents Rated 3 out of 5 stars

I completely agree with the very first comment left two years ago:
"It would be great to be able to add custom user agents, rather than the current very limited selection."
https://addons.mozilla.org/en-us/mobile/addon/phony/reviews/231528/

This review is for a previous version of the add-on (3.4).