Why is the invoice line item read-only?

[Naruto Fujimori]

I have received the product and have manually created an invoice.
Next I created an invoice line item, but it is read-only.
I would like to be able to write on the invoice detail to enter amounts, etc. Please let me know how to do this.

It is still in OOTB and has not been edited.
Note that I am logged in as admin user as shown in the attached image.

[Jeff Cies]

Hi @Naruto Fujimori, it sounds like you might be in the purchasing view, which was created by the SPO team for their workflows. For APO, we use the default view for all forms. So if you click on the "hamburger" icon in the top left corner and select Views > Default, you'll see some additional fields open. From there, you'll notice that the "Line amount invoiced" field is still read only, but you'll be able to add in Invoice Line Quantity, Unit, Line Unit Price, Subtotal etc...