No joy. That is part of the issue for me, actually.
I am on a Mac (OS Sonoma) and the ToDo app and Outlook app are not playing together.
From the ToDo app, f you want to see a flagged email, it will open Outlook on the browser, not the app (that is the topic of this thread).
But also, from the Outlook app, if I want to launch the ToDo (by clicking the checkmark on the menu list on the left, as David is suggesting) it will open ToDo on the browser, not its app.
It is as if on a Mac Microsoft doesn't want to link the two apps? I doubt this is on purpose, because nobody would switch from Mac to Windows just because of this, it is more likely we will dump ToDo. Outlook works very well, especially in a corporate environment.
How silly and annoying this whole thing is. Instead of coming out with useless upgrades every other day, Microsoft should just iron out these silly inconsistencies.... Apple would never allow this to happen with their products.
It is truly a different philosophy between the two companies.