I want to broadcast to an device in the network that is not the subnet-range of the local network-range. Both Mikrotik (router and Cap Lite) can see the the local IP in the ARP table.

The local network is in the 192.168.10.0/24 range and the WiFi network range on the Cap is 10.10.100.0/24 range and the ether connection has an in the local network range (192.168.10.50/24).

When I use Torch on WLAN I can see the broadcast being return but directly to the address in the local network and not to the IP address of the Wlan interface (10.10.100.150) as it is done when using for other traffic that is Natted.
I assumed because in the ARP table (bridge) in the he CAP, the broadcaster requester is know it should work but it seems I am missing something to have the broadcast answer also being delivered back to the device initiating it. I am using DHCP 82 on the WLAN side because of the DHCP server on the 10.10.100.253 device sending it's DHCP offers. And also on the bridge I have IGMP snooping active but to no avail (does not help).

It seems to be a really difficult one.

Don't claim to be the expert here, but as I understand it, broadcast only works on the local subnet. In other words, it will not route.

Thanks k6ccc and I have now tried one of the IP helpers in IP/Firewall/Service Ports. In connections it looks good this time however I don't see the answer anymore from answering device when I torch that interface.
Before the device answered but the requesting device was not reached.