Modifying scoped registries in project manifest does not update Package Manager UI window because a UPM Resolve operation is not triggered. For instance, adding scoped registry does not display it in PackMan UI as long as UPM Resolve is not called.

It is not a regression but with the introduction of the new submenu 'Packages > My Registries', the bug is more apparent.

Workaround:
Force a UPM Resolve by installing/removing a package.