Depending on your setup, you'll need to configure the 10.10.10.x network on phase2 selectors as local network on HQ and remote network on Branch. Also as @asonay suggested, will you need a route on Branch FW towards 10.10.10.x via the VPN interface between HQ and Branch. At the end, you need IPv4 policies on HQ and Branch as well to allow traffic ingress / egress between the networks.
I'm assume you use selector based VPN and no dynamic routing between HQ and Branch.
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