Stuart Clarke, There are ways to update the resources deployed as part of Managed Application deployment (in this case Meraki), for example, review the articles below:
- Work with resources in the managed resource group for Azure managed application
- Publisher and customer permissions
This should be done from the customer or publisher endpoint - mainly because it is not known - how application stores auth token. The parameter values supplied when creating resources are simply passed to the application deployment template etc., and it will be up to the application to use it as it seems necessary.
I would suggest opening a support ticket with Azure Support and seeking assistance from Cisco as well to explore options.