Web Interface to place orders

So, Im working on an App which lets users create a new order. Usually those get imported from CSV/API, but there should be an option for a manaual order via Retool.

Ive got adress selection and so forth working, but I want an elegant way to add the products and amounts to the order.

I have a DB with all available items which can be ordered. Then I want the user to be able to select which items he wants to add to the order and how many.

What would be the best way to work on this?

I was thinking of a table with all items on the left, row actions which add the item to a local variable/table(????) which is then shown on the right. How would i store/process that?

What also makes it more complicated:
Ordered items are not stored as:
Item A - 10 times but rather as 10 entries for Item A. So when the order is created there needs to be some logic to create multiple entries depending on the amount set.

Thanks for your help!

Sounds like a shopping basket to me, is that right? - there's lots of best practices and guidelines for that particular UX, I suppose it depends on what your current app looks like and how it would need to fit in. ie do you have space for a table or does it need to be a drop down, can you multiselect, what happens if you pick and item that's already in the table etc.
Depending on your needs there will be plenty of options to implement it - can you give a little more detail on your ideal outcome to help you find the right approach?

Sure, thanks for the reply!
I wont really be a shopping basket for an B2C end user, rather a screen where a shop manager will be able to create an order manually. Those manual orders are special as the reason why they have to be created manually is usually due to having many ordered items or requiring special things.

In any case, it doesnt have to be as pretty and user-friendly as a end user would like it, rather the feel and features of a more power-user like tool for the shop managers.

Right now im working with row actions, but im considering running the code on row double click or creating a ">" and "remove" button which will add the selected entry to the list of items in the order to be created