Custom firewall rule to route one lan ip to wan2

Installing and Using OpenWrt Network and Wireless Configuration
7

I did it this way:

config route
	option table '210'
	option netmask '0.0.0.0'
	option target '0.0.0.0'
	option gateway '192.168.34.71'
	option interface 'wg1'

config route6
	option target '::/0'
	option table '210'
	option gateway 'fd42:0:0:34::71'
	option interface 'wg1'

config rule
	option src '192.168.47.31/32'
	option priority '210'
	option lookup '210'

config rule6
	option src 'fd42:0:0:47::31/128'
	option priority '210'
	option lookup '210'

The source is 192.168.47.31 and fd41:0:0:47::31. All traffic from this source is send via interface wg1 via 192.167.34.71 and fd42:0:0:34::71 (this is the gateway).
Using a numeric table I don't need to add an alias to the rt_table configuration file.

It still requires routes from outside to this ip address ... and you should enable connection tracking for the zone with your device.
Any traffic from somewhere else than via this gateway (192.167.34.71) to the ip address (192.168.47.31) won't find it's way back.