I think there might be a bit confusion upon terminology here. When you create a new Network in an Organization using the GUI, you can choose between different Network types - type specific or Combined. If you create a network via GUI, and select Security Appliance, as the network type, using the API endpoint GET /networks/{networkId} should return ...
"productTypes": [
"appliance"
],
... If you create a new Network on your organizations, using API endpoint POST /organizations/{organizationId}/networks you can set the Network type in the field productTypes "productTypes": [
"appliance",
"switch",
"wireless"
], If you select more than 1 type in productTypes, the Network Type will become Combined. It is not possible to convert 1 network to a Combined, per se. What you can do is, if the Network does not contain the wireless product type yet, you can create a new Network as productType = wireless, and combine the new Wireless network with the original network using POST /organizations/{organizationId}/networks/combine
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