I love the look & feel of Supernova and hope there's enough momentum to improve the UX further and make it the one-stop free Outlook alternative out there. Hopefully I can contribute with this idea.
Limit the number of items within a contextual menu. (...) Keep the list length manageable by including fewer than 10–12 items, to avoid choice overload and ensure that all of the contextual options are visible, without having to scroll.
Right now, the email context menu of Thunderbird (v115 "Supernova") has 23 items (first level only, see screenshot). On my laptop screen, the list isn't even visible entirely. As a user I find that overwhelming.
Therefore, I suggest to simplify and shorten the context menu by categorizing the items into 3 types of actions:
And what about power users that want many actions easily accessible? That's a fair point, and I would argue that those would use the existing hotkeys anyway (like Ctrl+R to reply, or Enter to open in new tab, or K to ignore a thread) and do not depend on the (somewhat redundant) hotkeys from the context menu, so items could be removed.
Of course, it's always a trade-off. But if Thunderbird is supposed to gain more widespread popularity and appeal to average users, I'd opt for the suggested simplification. If there's interest, I'd also be happy to make a concrete suggestion on how to restructure it (without having usage data, though).
Thanks for considering and greetings from Munich, Germany.