UnMasquerade link missing

Problem/Motivation

Once Masquerading as a User, the Masquerade/UnMasquerade Block is not shown and there is no way to UnMasquerade apart from logging out and back in as the Original User/Administrator. This worked well in the Drupal 7 version, but is missing in Drupal 8 and 9 version.

User interface changes

Add ability to Block to UnMasquerade