I found a workaround, not sure this is the better way but it works.
I start from the following layout :
My networks are of Wireless type.
First I create a new network dedicated for switches. Add devices in it and configure it.
Then, I create the switch template in addition to the Wireless template.
I combine the templates to create a unique combined template.
Now I can combine the wireless & switch networks between them
Done !
Maybe there is another way to save time 😉
Many thanks to all