I keep toggling the preference full-screen-api.ignore-widgets via the Configuration Editor (i.e. about:config) and I'm wondering if Firefox would allow an extension to perform that change programmatically (upon clicking the extension's icon in the toolbar, for example)?
I've searched around a fair bit already, but could only find ooold answers (e.g. this approach from 2013, which I'm quite sure doesn't apply to modern Firefox anymore).
The answer seems to be a resounding "No, not in modern FF" - thanks to @nanigashi for clarifying.
The best way to ergonomically toggle/access a setting that I've found was to pin an about:config tab and/or find a short identifying substring of the setting name to enter in the about:config search (i.i in the case of full-screen-api.ignore-widgets)