This looks like it’s the most requested improvements that isn’t there in ideas. I know I have requested this at least a couple of times.
The following are all requests to do something like this
https://forum.manager.io/t/combine-customer-and-supplier-attach-files-to-customers/27090
https://forum.manager.io/t/linked-customer-supplier/10030
https://forum.manager.io/t/customer-supplier-account/9328
https://forum.manager.io/t/when-customer-is-also-supplier/988
https://forum.manager.io/t/when-customer-is-a-supplier-at-the-same-time/3783/3
https://forum.manager.io/t/sale-to-supplier-buy-from-customer/26724/3
https://forum.manager.io/t/same-supplier-is-customer-how-to-link-accounts/19913/2
https://forum.manager.io/t/merge-customer-and-supplier/24808
https://forum.manager.io/t/customer-and-supplier/20549/7
https://forum.manager.io/t/same-one-as-customer-supplier/16250
https://forum.manager.io/t/idea-enhancements-to-customer-and-supplier-accounts/24438
And I believe there’s more but I am too lazy to list them all.
However, @Tut have mentioned a valid reason why this is not done and that is the control accounts (which are very handy to control which customers/suppliers go into which chart of account entry)
But, I think there is a way to combine external parties without breaking the current setup. I think that maybe if you maintain the current tabs as they are and create a parent object that can hold multiple customers, suppliers, employees, capital accounts and expense claim payers, then you can have the best of both worlds, complete backwards compatibility as well as a way to summarize multiple account as one entity. This will also solve other issues multiple branches/addresses per customer.
Maybe you guys or @lubos can come with a better implementation but it shouldn’t be abrupt. It should be smooth.