Keycloak regex mappers

Hello.

We have a Keycloak and OIDC auth provider it is connected to.
OIDC provider on login within separate scope send us special claim in format <Software>-<platformrole>:<organization>

I want to add user to specific groups based on <platformrole> (one group per role) and <organization> (one group per organization).

Per my understanding I can user Advanced Claim to Role or Advanced claim to Group and use “Regex Claim Values”.

Something like “key:groups” with “value:-(.*):”.
And assign that claim to certain role.

But this part is unclear for me.
With that configuration Keycloak provide to underlaying software empty “groups” claim.
What else need to be configured?

Practically speaking I need to assign role to the user based on the part of the claim coming from IdP provider.