I made few changes and added a new project; after these changes -- my workflow now stopped showing drop down for status changes. I can transition using a button; if i can get drop down back again would be helpful.
Welcome to Atlassian Community!
Is sounds like you turned off the new issue view, if you see transitions as buttons instead of a drop-down. Click on your avatar up in the right-hand corner and select Personal settings, at the bottom you should see a slider that allows you to turn on the new view, this should bring back the status drop-down.