I use multiple tab groups, each assigned to a particular task or workflow. For ease of reference, there are some tabs I like to keep pinned. However, each of those pinned tabs appears in every one of my tab groups, e.g. the Mozilla HTML and CSS reference pages are pinned to the left edge of the tab bar whether I'm looking at my "Web Design" group, my "Coding" group, my "General Browsing" group or my "Gaming" group. Thus I'm limited to what I can pin without cluttering up the tab bar. The alternative would be to use still more separate tab groups for these reference sites, but that breaks my workflow.

I know this probably isn't the intended functionality of app tabs (the name is pretty suggestive), but is it at all possible to assign particular app tabs to particular tab groups? I didn't see anything in the Firefox reference materials saying so. Thanks for your time.