How can I make small cells under regular cells?

In calc, I need to to make certain cells an irregular size under regular sized cells (unless someone can explain to me that it is not necessary!) I am creating a duplicate form:

image

from this form…

image

However, the only solution I can come up with is to copy and paste the vertical “vendor” as a picture. I can’t figure out how to align the cells up so that I can have many cells on just that row underneath the normal cells on top.
Do I need to merge a large number of cells on top first, and then I will be able to use unmerged cells below to get the desired result?

Yes, it is a real solution.

(You can not divide an unmerged cell to some smaller parts.)

Who is designing such funny labels? Are they prescribed?

You may try it as demonstrated in the attached example.
Whether you create a form, and connect to a DataBase (other contributors can advise better) or just use FormControl objects to be able to freely position and size cell-like objects, I would suggest you enter or prepare by calculation the contents needing to be displayed somewhere, and to pull the results into the display area by defining linked cells for controls.
disask83778DeclarationKindOf.ods (36.7 KB)

What do you need for this form? Do you need to work with fields (forms)?
Why not with tables in Writer?