If it’s used to change parameters of default route from dhcp, you can add static one (1.1.1.1 is any random address, it won’t be used):
/ip route add dst-address=0.0.0.0/0 gateway=1.1.1.1 comment=dhcp1 routing-table=Starlink disabled=yes
Then set add-default-route=no for dhcp client and use lease script to update the route you added, e.g.:
:if ($bound=1) do={
/ip route set [find where comment="dhcp1"] gateway=$"gateway-address" disabled=no
} else={
/ip route set [find where comment="dhcp1"] disabled=yes
}