When exporting compositions krita seems to use PNG by default, and the last used settings for the last export you did. This makes it simple yet cumbersome if you need to make changes to the export image type. Its not very flexible. Common settings are JPG, PNG , alpha or not, Background color and more... The easiest would probably to show a prompt where you make your choices? I'm open to other solutions too.
*** Bug 417500 has been marked as a duplicate of this bug. ***
I still would like this very much