we have an area for "products" where you can input (manually) a list of items, so later on it's easy to include them into your invoice

Is there a way to bulk add?

you mean the products in the product list, or the "stored" products into the invoice?

the products have to be added one by one into the products list. then you can go to the invoice and simply start clicking on every item you want to include in the invoice and it will be added. that process is not "bulk add" but it's really fast.

I like the idea of selecting pre-built item to add to the invoices. I did mean the ability to import a large number of items to be added to the list of items. I'm not sure if custom field types are possible (like product name, serial number, manufacturer, etc) if possible.

no, sorry, that kind of "bulk addition" is not available, not out of the box.. (how many items you need to add? just out of curiosity..)
also, the items have only "name" and "description" (also price, amount, discount), but there's no room for these other custom fields you mention. not out-of-the-box, anyway)

best,
Germi

Oh, okay. Sounds like a custom request. I have a client who is starting an equipment repair business that involves submitting a quote for parts. It can conceivably be hundreds of parts. It would be good to also somehow be able to categorize items to keep them organized. Thanks for your help.