Heyo!
I have made a free plugin that lock actors in the Editor Viewport. I will release this plugin in Marketplace, but right now you can check my GitHub repo and download latest release. I have built it only for UE 5.1, but older version will come soon. There is still plenty work to do and improve, but I hope it will help you.
UPD: Added UE5.0 support
UPD: Now the plugin is available on Marketplace for free