Just to possibly save others some frustration...

As of ROS 3.10, winbox does not know about layer 2 meshes, so the cli must be used.

One of the cli settings that you will be setting is the 'wds-default-bridge' setting on the wireless interface; you need to set it equal to the mesh interface you created.

If you happen to open up the wireless interface and check out that setting, you will note that the drop down box does not list the mesh interface you created. That is because winbox does not know about layer 2 meshes, so it does not know about the interface you created. That is why the cli has to be used to set that default:
/int wireless set wlan1 wds-default-bridge=mesh1

Here is where the frustration comes in... If you later use winbox to make any changes to that wireless interface, winbox will remove the 'wds-default-bridge' setting, changing it to 'none'.

So, if you use winbox to change the wireless interface, it will break your mesh until you go back into the cli and re-apply the wds-default-bridge setting.

Hope that helps someone!

This is a bug? or what?

Thanks!

No so much a bug... but rather that winbox always lags a bit behind the cli feature set. Usually, winbox laging just means that some new features are only available through the cli. But in this case, the lag can unexpectedly mess up settings done through the cli.