Failover LAGG primary interface selection missing

[BertVano]

Hi,
I am using OPNsense 3.7.12_5.
I want to set up a failover LAGG interface using the web GUI but I am missing a selection box to set the interface which is supposed to be the primary one. When selecting from the drop-down,  they're ordered alphabetical and the first one will be primary/master. Evidently I need it to be the other one, as it has a higher speed (10G vs 1G).

How can I set this up?
Thanks in advance