Open Other Settings → Misc in the search sidebar and check "Do not show Accounts in Collections / Favorites". Search results will then exclude every creator who is already in one of your collections or favorites — ideal for discovering only new faces instead of profiles you have already saved.
The opposite direction is available too: Other Settings → Filter by Collections restricts the results to creators who are members of the collections you select, e.g. to re-filter an existing shortlist by new criteria. Both settings combine freely with all other creator and content filters.