It is kind of frustrating what Apple says that about adding a location for Calendar events:
If you select a location from the list, a map and weather info are added to the event. If you just use the location you entered, map and weather info might not appear.
If the event info window includes a map, an alert is set so you’re notified when to leave to arrive on time at your destination.
So if I use a drop down option but want to add a room number or floor in the building, this event will lose integration with Maps.
However, I found a workaround using iOS devices. That is, type the location as you would on iOS Calendar app, then both Mac and iOS will recognize the location, and tell you about weather info, and remind you on the Maps app.
But do you guys have a smarter way?