You have a very good point. There's little documentation around on how to do the two things you mentioned: (1) initializing a database (e.g. from another accounting system) and (2) keeping the database in sync with a second administration (such as your shopping cart).

There are a few somewhat hidden import features; depending on your use-case, that might be enough - or not.

* Import of a Chart of accounts - allows one to initialize all accounts without creating them manually one-by-one

  Can be found under "General Journal > Import Chart of Accounts"

* Import of a journal entry - allows one to import a (large) journal entry without manually entering it

  Can be found under "General Journal > Import"

* Import of Goods/Services/Overhead - allows one to bulk-define goods(inventory-based parts)/services(non-inventory parts)/overhead

  Can be found under "Goods and Services > Import"

Inventory can be imported through "Goods and Services > Import > Inventory": it will set up the accounting correctly to account for the cost of goods sold on sale and add to the inventory asset account. There's one thing though: I've overhauled the code which does the inventory adjustments through the UI, but from the first look at the code, it seems this code wasn't part of that rewrite. I'd love to help you to address that problem when you run into it though.

Regards,