Field of child table not visible

In the item doctype there is a child table to store a barcode of the item. The barcode is edited inside a child table. The table/doctype has three fields: baecode, type, uom. The field for the barcode is not visible. It is missing in edit row pop-up as well. Can anyone give me a hint how to make that field visible again? We used it before and there are a lot of items with stored barcode.

ERPNext: v14.x.x-develop () (develop)
Frappe Framework: v15.x.x-develop () (develop)

Hi @knudeh,

Please check the step in Image.

Then reload and check it.

Thank You!

Thank you for your reply. I know these steps.
Inside step 2 there is only Barcode Type and uom to choose from.

Any other guess?

Hi @knudeh,

Please check it.

Thank You!

Thank you. It is visible again.
First thing: use customize form not doctype. Yes there is a big hint.
Columns is for all three fields 0, that was not the problem.
For barcode there was hidden checked. Unchecked hidden and it is visible again.