Here's how I'd approach it, in order of effort vs payoff.

Step 1: Use what's already free inside WhatsApp Business (do this today)

You may be underusing native features that solve half the problem:

• Labels: WhatsApp Business already has chat labels. Create stage labels (New Lead, Quoted, Advance Paid, Design Sent, In Production, Payment Due, Delivered) plus size labels (Small, Medium, Big). You can filter chats by label. This is literally what your extension idea does, for free.
• Quick Replies: save your catalog intro, branding explanation, payment terms, delivery timelines as "/" shortcuts. Cuts typing time massively.
• Catalog, greeting message, away message: reduce the repetitive first messages.
• Linked devices: the app supports your phone plus 4 linked devices (WhatsApp Web/Desktop on team computers). If you're hitting that limit with more than 4 people, that's the real signal to move to the API.

Step 2: The Chrome extension (good idea, worth building)

Since labels already exist, make the extension do what labels can't:

• A Kanban board view of chats grouped by stage (reads labels or its own tags from the WhatsApp Web DOM)
• Show "days since last reply" so stale leads surface
• Highlight chats waiting on you vs waiting on customer
• One-click log of order value so you can see pipeline totals by stage

It's non-invasive as long as it only reads and displays, and never auto-sends messages. Auto-sending from WhatsApp Web is what gets numbers banned. I can help you build this. It's a weekend project: a content script that scans the chat list, stores tags locally or in a shared Google Sheet, and renders an overlay panel.

Step 3: A pipeline outside WhatsApp

Chat is not a CRM. Even a simple Notion board or Google Sheet (customer, phone, stage, value, advance received, design status, expected delivery) that the extension pushes to gives you reporting WhatsApp never will. You already run analysis in Notion, so this fits.

Step 4: WhatsApp Business API (when the 4-device limit or volume really hurts)

The API gives unlimited team members on one number through a shared inbox. Since late 2024, replies to customer-initiated chats are free on Meta's Cloud API; you only pay per message for business-initiated template messages (marketing/utility). If you connect directly to Meta's Cloud API there's no mandatory subscription, but you need a developer or a self-hosted open-source inbox like Chatwoot. BSPs like AiSensy charge a monthly fee for the ready-made inbox. Trade-off: the API number can't be used in the normal app anymore, and there's no built-in catalog browsing experience like the app.

Step 5: AI agent (do it in phases, not all at once)

Don't start with an AI that texts customers directly. Start with AI that drafts and a human sends: