The user may modify the list of workspace tags that results form
applying the dynamic order. This way one may filter workspaces they
don't want in the order (e.g. "NSP") or apply any transformation he
wishes to the list of tags.
Note this is very similar to the function of the same name exported by
DynamicWorkspaces. Ultimately it would probably be cleaner to
generalize the one in DynamicWorkspaces to accept an arbitrary
workspace sort as a parameter; this is left as an exercise for future
hackers.
