I use the iPad OS 15 beta, iOS 15 beta and OSX Monterey beta. One of the features added is that remainders have support for tags. Please give os opportunity to set tags for the remainders vi create from Agenda.
It’s unfortunately very unlikely that Apple has made tags available to 3rd party developers. It’s a big shame that they’ve been adding a lot of functionality to the Reminders app in the last two releases that they don’t allow us to get access to through the interface for developers