T6679 added support for destination groups in NAT66 for DNAT and T7051 ported support over to SNAT, but neither addressed adding support for source groups.
set nat destination rule 10 source Possible completions: address IP address, subnet, or range fqdn Fully qualified domain name > group Group port Port number
set nat66 destination rule 10 source Possible completions: address IPv6 address or prefix to be translated port Port number