Similar to the request to group workspaces and repositories (https://plasticscm.uservoice.com/forums/15467-general/suggestions/2772036-group-workspaces-and-repositories) but not quite the same.

Using submodules to group repos limits you to a single classification of a repository. Ideally you are able to tag a repository with several keywords like you do on a forum or an article. This would allow us to tag a repository with 'real-time control' or 'imaging algorithm' but also tag it with a product name that uses it or the programming language that it is written in.
This would necessitate a new repository view in the client where instead of a list of repos you get a tree view list of tags which expand to show the repos that have that tag.
To set the tag, a right click menu 'Add Tag' would need to be added to the normal repo view.
Having this feature would allow easy navigation of many small repos and further encourage use of the Xlink feature.