this feature , allows to give the capability bgp label-unicast to set the multipath :
vyos@vyos# set protocols bgp address-family ipv4-labeled-unicast Possible completions: +> aggregate-address BGP aggregate network/prefix +> network Import BGP network/prefix into labeled unicast IPv4 RIB
example on FRR :
address-family ipv4 labeled-unicast maximum-paths 4 maximum-paths ibgp 4