If I create a customer in Business Central, I can make it sync to D365 for Sales (Account).
How can I make an Account from D365 for Sales appear in Business Central?

If I create a customer in Business Central, I can make it sync to D365 for Sales (Account).
How can I make an Account from D365 for Sales appear in Business Central?
The account in D365 Sales needs to have its relationship type set as Customer. Relationship type out of the box is not on the account form so you may need to add it. Once you've done that the sync will then add it to the sync tables, if you then create a customer in BC, don't add any details and select coupling you can then connect it and sync with the account in D365S.