To create client tags, got to Scheduling>Global Settings>Entity Tags and create a tag for the tied entity Client.
To add a tag to a client, see Client Profile>Demographics>Other Fields, choose from the Tags dropdown, and click Save Client.
Note that the tags field existed previously as a free-form field. Any tags created before this release have been converted to standard tags in Scheduling>Global Settings and left untouched in each client's profile.
Once tags have been added to a client, it will be visible at a glance in their profile thanks to the tag icon next to their name. By hovering over the icon, the specific tags which have been added to the client can be viewed:
You can filter on client tags in the Clients list:
and in any shift approval list, where hovering over the tag icon next to the client name will show you any tags associated to the client: