By pressing alt-K the abctajpu popup will appear, and if the first checkbox is ticked (⚡) then you go straight to the first text entry box (for macros) and when you enter a valid macro the popup automatically closes and the macro expansion is inserted into the page. For example if the abctajpu options defines macro c=ĉ and the ⚡ is ticked, then typing alt-k c will insert a ĉ. The choice of alt-k should be configurable by the Firefox brower itself (it's easy to find in Chrome, but seems to be missing in current Firefox). Also, due to Firefox bug 1324255, instead of typing alt-k c, you currently have to type alt-k tab tab c (hopefully this will be fixed soon). Note that Firefox on Android works a little differently.