I have been a Wireguard user for many years now. But Today I Learned you can configure “PreUp, PostUp, PreDown, PostDown” scripts just like a normal Linux network interface. I am using this on a Proxmox server to make sure IP Forwarding is enabled whenever the Wireguard interface is up.

[Interface]
PrivateKey = [hidden]
Address = 172.16.0.13/24
PreUp = sysctl net.ipv4.ip_forward=1
PostDown = sysctl net.ipv4.ip_forward=0

The only place I can find this documented is in the wg-quick man page, found here.