Though maybe moot with the proposed new functionality mentioned by Nick, but still:
Just to put it out there.
I admit I have uploaded a few flows too which have dashboard items.
People have said that it is/was not fun/nice because it causes unused things after testing/debugging.
Maybe it would be nice when you delete tabs/groups that as they are "empty" they get auto deleted.
I get that when building a new group the group will initially be empty, and so it would cause a problem with handling it.
But as a thought to get around that, a new way of building a group would be used.
Not too difficult. Here is how I see it would be done:
Drag a dashboard item into the work area.
The red triangle will appear.
Create a new group and all is good.
That way is not too different to the way which would cause the problem with the way I suggested is to create the group prior to dragging the dashboard item into the work area.
Just a thought.
With this way an automatic tidy up could be applied to happen automatically.
As a final option: This could be turned on/off so if people want unused groups (etc) then there is no problem.