The State Tree Diagram was available in the 9.x days. A work around with the registry key kept it working in 10.x. Since development has all but ended in traditional desktop, it's time to bring this request forward to ArcPro.
SDE administrators rely heavily on this tool. Period. The health of SDE versioning in general is dependent on congruity of the States and the Lineage. This need will not disappear with ArcPro or with branch versioning.
Esri, plan now. Work now. Get this accomplished.
To work without the State Tree Diagram is like you having to write code without a computer. Not very productive, intuitive, or feasible. For SDE administrators, the State Tree Diagram is a requirement, not a nice-to-have.
SDE management. It's a thing in GIS.