Issue has been identified and a fix is being made. It will be rolled out with the next update of SSMS 18.
Same issue here. I'm using Win 7 Pro
5 votesLucien commented
I have the same issue. When setting up a new session either through wizard or new session, when I get tot he event filters (Configure) and click on the Field, the drop-down list appears momentarily on the top left corner of the screen and then disappears.