I also has the same exact problem in KDE. Even the shortcut for konsole is also gone for me right when the issue start. Plus the usual Manjaro updater and Pamac trayicon are also gone. I tried to do a fresh install two days ago and it happens again right now.
After reading here and there, I found a solution for me. It seems this whole problem happens due to git dependencies being installed in the system. Actually there were two problems that I had face and solved them using this method here:
Major stuttering in KDE:
Network unable to connect:
It seems everything works fine now. I think this won’t work on XFCE though.