Firewall rule to hit my VPN (outer) traffic

[Vetal]

I have my tinc running on pfSense.

Unlike OpenVPN, which has control over gateway group, VPN runs on, tinc does not and it goes via default gateway

Now I need to add failover line which is metered but way less congested LTE to pass my Tinc traffic over it

I can't find the way to add it since it is not going via LAN

Did some tcpdump-ing, it runs on my WAN

Sometimes,

my_wan_ip:tinc_port -> remote_ip:tinc_port
remote_ip:tinc_port-> my_wan_ip:tinc_port

Sometimes,

my_wan_ip:some_high_port  -> remote_ip:tinc_port
remote_ip:tinc_port-> my_wan_ip:some_high_port

Where "tinc_port" - port I set up in settings (==have control over)
some_high_port - some port > 60000 chosen by tinc on pfsense.

It seems like there is no control over this high port.

But the main issue, where to set this rule with gateway override?