I have updated your source a little to use the VForm, VFields, DataSource. This is the
recommended methodology.
This is what I did.
1. Added a VForm to the layout. I placed this on the column next to the data-table. These are the properties I set for it,
2. Added 2 VFields inside the VForm, these are txtarticle and cboum. I set the field names to be 'article' and 'um', gave them titles. For the txtarticle, I specified
This will show a text field on the form and also a text field for inline editing on the table.
3. For the combo box, I specified the field name and caption, title. and set
This will show a combo on the form and also a combo on the table during inline editing. I left the key & value fields untouched.
These indicate which fields should be used for the key (item value) and value (item text)
4. Added a data-source. Didn't specify any property for it.
5. Update the data table Manual property to be true and removed all the other properties you had set. That is all is needed for the automatic binding of the form to the data-table and data-source.
6. Added some items to the combo on mounted.
Note that is is using the item-value & item-text indicated above.
Dim um As List = page.NewList
um.Add(CreateMap("id":"LT", "text":"LT"))
um.Add(CreateMap("id":"PZ", "text":"PZ"))
cboum.SetItems(page, um)
The final result
Source code attached!
PS: I know you are not a fan of videos so much

, but this methodology can be
watched in simple short videos from
Creating Vuetify Forms using BANanoVuetifyAD3 - Part 1, where we look in details step by step how to create forms and we look at all the options of the data-table, form controls etc.
All the best.