I had the same issue yesterday 14.03.26. The right click on Audio option did not work, there were barely any options. However, Hontr above made me think about whether there was an issue with the connection. Basically, after OBS stopped working due to an update (always seem to affect me) I had to reconnect to Youtube. I did all of this and the 'Manage Broadcast' button vanished. When I disconnected and re-connected the stream key using the wizard, it looks like, I did not authorize OBS and Youtube to talk to each other. I went back into settings and stream, re-entered the stream key, entered and the authorization box came up, I agreed and now my Manage Broadcast button is back. Hope that helps someone.