I'm trying to rebuild a few "apps" that were originally built in SharePoint 2010 using SPD Workflows and the built-in "Approval" workflow. The whole "modern approval" process seems like the best thing since sliced bread; people have been clamoring for years to be able to approve via email. However, in most of our existing solutions, we are assigning the approval tasks to SharePoint Groups (which doesn't appear to be supported in Flow at all), getting them from another list (e.g.: a staff contact list where each person has a designated 'leave approver' which may or may not be their AD-designated 'manager'), or assigning to a person specified in the item (e.g.: students fill out a request form and specify their instructor who must approve the request).
Now, the last method seems pretty straightforward, but the others...not so much.
In the first case (assigning to SP Groups), I've read that the suggestion is to use O365 Groups. I'm not opposed to that, but when I enter a Group's email address in the 'assigned to' field, it doesn't resolve (it seems to only accept actual users, not groups). So, if an Approval can be assigned to an O365 Group, can someone tell me specifically how to do that?
The second case (getting the approver from another list), I would think that we could have Flow go to that staff list, retrieve the approver, put it into a variable, then drop that variable value into the 'assigned to' field. However, the "go to that staff list, retrieve the approver" step actually gets fairly complicated. The interface for pulling values from other lists/libraries is so minimalist compared to what we could do in SharePoint Designer.
The bottom line is that we really want to ditch SPD Workflows (and InfoPath, but that's another story) in favor of Flow (and PowerApps), but it's just much more complicated than it should be. Building a SPD workflow is like snapping together Lego bricks; it feels like trying to do that same thing in Flow is more like starting with tiny grains of plastic, melting them down, making the mold, then forming the bricks before they can be assembled.