The supported method of accessing Google Dialogflow CX agents from multiple Google Projects is to use the Consumer Project and Resource Project model as described here: https://cloud.google.com/dialogflow/cx/docs/concept/multi-project. In summary the Dialogflow CX agents are in the various Resource Projects. The GCP Service Account entered into Genesys Cloud integration belongs to the Consumer Project and it can be granted permissions to the CX agents in the other projects.
However that won't work for your intended use case since all Billing is determined by the Consumer Project so this configuration will not allow you to keep the billing separate. I think you'll need to submit a feature request for increasing the number of Dialogflow CX integrations that can be installed in Genesys Cloud Orgs.
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Brad Wehmeier
Lead Software Engineer
Genesys - Employees
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