If you do "updates" it will give you an error on each extension not in the repo.
You can delete these extensions.
hi gerald_clark,
but there are situations that can lead to wrong evaluations and misconfigurations:
f.e. the network-connection fails temporary on one side (local or at the repository) or the respond is delayed.
so it can happen that for some package-update-requests these packages are reported as missing,
although there are still in the repository...
and perhaps fundamental packages are deleted afterwards by novice users...