In case when 2 keys are present in keystore, then alias-filter (filtering into single key) on key-store resource has to be specified, otherwise key-manager can't be created. If user want to use keystore with multiple keys, user has to configure multiple key-store elements with specified alias-filter (filtering into single key).

That is pretty inconvinient. Probably introducing alias attribute on key-manager would be more intuitive solution to this situation.

/subsystem=elytron/key-managers=server:add(key-store=server,algorithm="SunX509",password=key-password)