Since Quantum all extensions in Firefox are standard web extensions, which means some functions are no longer available (for example smooth abcTajpu inserting into the address bar or search box ). That said, macros do work for the websites I tested on (and tested on Windows 10, Windows 7, Android). Please check the format is good a=b|c=d etc, and if still a problem send me a URL to test on. Some (complex) sites do interfere with abcTajpu (alt-k and especially alt-x), so it can't be expected to work everywhere (but at least the clipboard should get populated).
Alt-k just starts the popup (which is the same as pressing the green abcTajpu button on the toolbar). Firefox can't yet remap keys, so if alt-k is already assigned then pressing the button is all you've got.
Favourite languages can be configured in the third options entry by putting a comma separated list of language codes, for example for French and Spanish enter fr, es (note there is a space after the comma).