Under Manage Jenkins -> Configure Credentials -> Providers I previously had 3 Providers: (Jenkins, User and Folder). With this environment, I only have 2 Providers (Jenkins and User), the folder Provider is missing in the list and I am not able to assign Credentials to folders.

I am sure this functionality has not been removed because the version history of 5.13 states:
"JENKINS-36160 - The credentials provider was not considering the folder as an itemgroup when accessed as an Item."