Can anybody recommend an add-on which works well with current (as of 2017) versions of Firefox to let you resize your browser window to a range of preferred sizes?
(I am ideally looking for an add-on as this is an OS-neutral solution, or, if it should be an appropriate alternative, a suitable helper program that would work to provide similar window sizing functionality for Linux and/or MacOS.)
The well-known Firesizer add-on unfortunately requires an additional add-on to provide an add-on toolbar, as the Firefox developers unfortunately removed that functionality, to the annoyance of many users.
Firesize seems to be a fairly nice alternative, but unfortunately it seems to work a little erratically and requires delving deep into add-on preferences to add new custom window sizes rather than being able to do so quickly and easily via its toolbar icon.
Thanks for any useful suggestions.