It would be also OK, if WG client/GUI interface would support PostUp/PostDown options:

PostUp = ip route add 192.168.1.99 dev wg0; ip route add 192.168.1.54 dev wg0; ip route add 192.168.1.155 dev wg0; ip route add 192.168.1.8 dev wg0;
PostDown = ip route del 192.168.1.99 dev wg0; ip route del 192.168.1.54 dev wg0; ip route del 192.168.1.155 dev wg0;