Do you have to have the Where? If not, .Tree is the easiest, but it doesn't love being paired with a Where.
If you need the Where, one thing you may consider is using code to build your hierarchy. This will give you full control. This isn't exactly related, but I found this a few years ago, and it is handy https://community.onestreamsoftware.com/t5/Implementation-Q-A-Archive/Question-Can-I-create-a-dashboard-dropdown-or-list-box-which/ta-p/1335. This post shows how to build the hierarchy.
Hope this helps!
Tom