When using a messaging tool like Assembly as a client portal wrapper, where does the actual client data (like tax documents) reside?

One member explained that although they use Assembly (formerly Copilot) as their client-facing messaging/portal container, the underlying documents actually live in Google Workspace. They embed their Google Workspace folders directly into Assembly, so when a file is dropped into Google Drive it automatically appears for the client in Assembly. This replaced an earlier setup where they manually moved files from Google into Assembly, which was described as "annoying."