On 6.5.2020 3.57, Daniel Miller wrote:
Does Dovecot presently support the MULTISEARCH command, or are there plans to do so?
If you mean RFC7377, that is not supported.  ref. https://www.imapwiki.org/Specs


I would suggest evaluating if searching a single virtual folder could work for your use case. ref. https://doc.dovecot.org/configuration_manual/virtual_plugin/

br,
Teemu

---
Daniel