[knot-dns-users] ZSK/KSK Key algorithm rollover

Hi, I'm in the process of changing the key algorithm from the former Knot default of RSASHA256 to the newer default ecdsap256sha256. For this I have just updated the DNSSEC policy and reloaded Knot. This created a new ZSK and signed the zone with this new ZSK, but also with the old one. Now the zone is signed with two ZSKs. How can I get rid of the old ZSK? I already tried to set "retire" and "remove" on the old ZSK with keymgr to a value in the near future, but that just lead to the error message "keys validation failed (missing active KSK or ZSK)" when issuing a zone-sign to this particular zone. So I'm stuck now. Additionally: How can I do a KSK rollover to also change the algorithm from RSASHA256 to ecdsap256sha256? I couldn't find a documentation explaining this step. I know that I need to have two KSKs until the DS record on the parent is updated pointing to the new key, but I don't know how to create a new KSK with Knot. Thanks in advance for explaining the process. Cheers, Tobias