Glad to see that this thread is relatively recent. I want to take some time to highlight why this is important and provide a visual example for what this needs to look like.
Pinning tab groups is an important idea that lets you keep collapsed sets of commonly used tabs, often organized by thematic area. While having a few tabs pinned is useful, the graphical representation of these tabs (example at the top of the image) doesn't allow for clearly understanding what is within each tab (examine the verbosity of example tabs under Personal, Academic, and Socials). Using pinned tabs without groups gets clunky when I have to manage 20+ frequently accessed tabs on a regular basis. Imagine the use case where, I have to manage a personal calendar, email, and notes + an academic calendar, email, and notes + several social media profiles.
There is UI precedence for this idea: ARC browser's main paradigm shift is the idea of 'spaces' or windows that separate your cookies/saved logins. Within a personal space, I can easily have pinned tabs in groups such as banking, blogs, and comics. Within an academic space, I can have common documents, slides presentations, and research papers in addition to communications. Whenever I need to freelance or start a project with another account, I can create a new space with pinned tabs.
With ARC browser being deprecated in favor of an AI project that is no longer centered on viewing web pages, I have the impetus to return to Firefox.
Firefox currently partially supports resurrecting a group of tabs. By clicking "List all tabs" I can hunt down prior Tab Groups and instantiate them, however, I would much rather have a set of pinned Tab Groups collapsed and ready for expansion and use at any time.
The desired user flow of this feature for me would be to right click on a tab group, then, in the "Manage tab group" panel, have an option for Pin Tab Group.
With ARC browser being deprecated, I'm now returning to Firefox, trying to find a way to make this work.
Like we have option of "sticking tab to edge", having the option to stick Tab groups to edge will be useful. We should have the option to stick the Tab group in these cases:
When the group tabs are collapsed into the tab group.
Only the Tab group label.
When the tab groups are expanded.
PS: Making it compatible with tree style tabs would be great to have!