Hello, for me it was enough to clear UI Builder cache based on this comment from user Ivan M Re: Why isn't my custom component appearing in UI ... - ServiceNow Community   

Hello everybody, seems like it is present in the "Zurich" release, you can create an app by importing it from source control:  or then link to source control when the app is created (it is located in app details): and when linked to source control th...

Hello, I'm joining with the same questionwill there be "servicenow studio" source control integration? it seems like a pretty important feature I think and it looks like the old studio will eventually stop existing/working - https://www.servicenow.co...