Since the long-standing issue of not being being able to assign clusters to Workspaces
https://github.com/rancher/rancher/issues/36132 is still present and Ranchers approach seems to be to ignore it
https://github.com/rancher/dashboard/issues/7734 what is Ranchers recommendation for users that make use of custom workspaces? Delete all clusters and import them again to the default one? Let the clusters remain in the custom workspaces and hope stuff doesn't break in the future?