I tried katalon is very similar to kantu, it it based on Selenium IDE.
On katalon there is not the bug of “Error #101: Kantu is not connected to a browser tab” It’s possible to run a macro from internal page of firefox without any problem (I tested this).
I runned macro from about:config or about:blank of firefox and the macro run perfectly from any page.
Why kantu do not allow to run macro from a non web page of firefox ?
it is very annoying not to be able to start a macro from any firefox page I hope you can understand how to solve this problem Katalon and apply it to Kantu.