Client Management Outside of WP Users List

I would like to have a Client Listing on the top level of the WP admin menu.

It felt a bit strange to have to add a new invoice, to find the “add a new client” function. Currently, QuickBooks online lets you add clients independently of adding an invoice.

Similar to adding a new WordPress page, the Client Listing would let the WP Admin Add a New Client, Delete a Client, Edit a Client. The Page could list all clients, and in the grid show a past-due summary by client, let me create a new invoice to the client. I could search for a client by First Name, Last Name, Client Name, Address, or Phone Number. It would be nice to see if I billed Client A, B and C, for this month, but I have not yet billed client, D, E, and F, so I don’t miss anyone in billing; even just listing the clients in a grid posted to the screen statically can help me keep track of which client I need to bill next as I run down the client listing.

Perhaps I can click on the detail view of the client in the listing, and see an itemized list of the invoices for this client, and edit the client details (name, phone, email), and mark a client as inactive, and mark if the client wants paper/mailed billing (so I can remember to print it).

The current Add New Invoice > Add New Client only allows for one address. It would be nice if I could have a billing address separate from the shipping address, and a phone number.

It could also be great if I can tie multiple user accounts to one business (ex 1: The client project manager wants to watch payments and pay them when the accountant is sick, but maybe their accounting person wants to make the payments normally; ex 2: A husband and wife need to pay the HOA account balance for a shared property, so either person could login with their own email/user account and pay the bill for the one client account).

Thank you. I appreciate your time.