Thanks Ilan and Aroop for replying. So not exactly move but rather *update* the existing set of rules so future replica placement will enforced by them. I managed to do so using the MODIFYCOLLECTION <https://lucene.apache.org/solr/guide/8_3/collection-management.html#modifycollection> action:
http://<hostname>:<port>/solr/admin/collections?action=MODIFYCOLLECTION&collection=<collection-name>&rule=shard:*,replica:<2,host:* -- Sent from: https://lucene.472066.n3.nabble.com/Solr-User-f472068.html