I would love to see a "Planner" tab when I open a group on Outlook
Most groups we use in my organisation are for specific projects, so we also use planner for each group. And what can be useful for us, is to have also a planner tab (near : conversations, one-note, files,...) that when we click on it, shows directly the planner board for that group.
As every plan is an Office 365 group, you can just browse through the groups/plans directly in Microsoft Planner.
Gary Lundblad commented
I agree that this makes sense. Planner is a kind of hub of sorts, for the team, but even more naturally, and successfully, within Teams, but Outlook is my personal hub for all of the things I'm responsible for. So what you're suggesting as a solution doesn't really fit the need.