How do I add many serial numbers at once in Aicountly Inventory, and does registering them create stock?

In the Serials screen under Masters, use Bulk add and pick the item. You can paste a list, upload a CSV file and map its columns, generate a range, or scan the numbers with a scanner.

For a range, enter a prefix, the From and To numbers, the digits for zero-padding and an optional suffix, then click Add the range to the list. Numbers already registered for that item are reported back and skipped, not duplicated.

Registering a serial does not create stock. Stock is created by a posted receipt document, and editing a serial by hand only changes the record of where it is.