Routing over different IPSec tunnels based on source IP

I think you could use an SDWAN route with Source Network (ex 192.168.1.0) and then set it to use Primary/Secondary and set your tunnel (ex 10.10.1.0) as Primary and None as Secondary.

Thanks for the reply. Can't do this as SDWAN routing is only for Gateways and an IPSec tunnel isn't a Gateway

I haven't tried it, but I use a 6in4 tunnel and have made the (IPV6) far end a gateway and it appears as an option in (IPv6) SDWAN routes. But it may or may not actually work, and IP tunnels may be different than 6in4 tunnels.

[EDIT: Now that I think about it, the far end of each of your tunnels is the same (10.10.1.1 or some-such) and since the Gateway is managed from the appliance, it can't tell the two apart. (It can tell the two tunnels apart, but not the Gateways which would appear to be the same from on-appliance and wouldn't have the SDWAN's "From" context to differentiate them.]

Is your site to site vpn policy based or route based?

With Policy Based you have to set source and destination networks.

IPSec tunnels