I’m aware this is an old question, but at first it didn’t clarify the issue for me, so I thought I’d add some more specific info about how to do this, because it might help others like me.
You need to select the “set members…” node, and then choose the pins you’d like to access in the details panel:
In the same way, you can also hide all the nodes that are not connected on large structs, and make your blueprints much easier to read:
