I've noted a couple of differences with Selection Explorer that may or may not be by design:
I have Selection Explorer ‘stacked’ with the View Filter Manager and Project Explorer. Often when I select the Selection Explorer tab (repeatable the first time after opening a project), any selected objects are cleared. Video attached:
Secondly, the Selection Snapshot appears to update automatically as selection changes, where previously required clicking Selection Snapshot. Is this by design? I used to be able to make a Selection Snapshot and select/edit objects from the ‘snapshot list’ while the list would retain the original snapshot. If I select/edit an object now, the ‘snapshot list’ updates to the one object. I find that I’m re-selecting the selection set repeatedly, which is frustrating, particularly when I’ve made an Advanced selection. I could save the selection, but often the selection is only required to complete the process at hand and I don’t need/want to save.