in V/05 - you said that you are able to see INCo1 - which is an incoterm 1 field on the right side or on the field catalogue by doube clicing on it.
the field will come to left side and after shifting the field
chec whether the field has got added to your condition table desired.
I dont think you can add new fields to the condition table once you have activated the condition table.
SAP says you can only make limited changes to the condition table, like changing the description, fast entry screen, header and footer fields, but not able to add new fields to the table, and I think that is the correct approch or else for the same table you will have two sets of condition records.
Please refer to the below link:
What you can do is create a new condition table with additional field and assign this table before the currently used table in the access sequence.
Hope this helps.
It is not possible to add a (new) field to an existing condition table.
By adding a new field to an existing condition table you are changing the structure of the table. And this is not possible.
Even if you would be able to do this you will run into issues when transporting the (new) table to either Quality and / or Production. Been there, done that. Lot's of issues to deal with.
The best way is to create a new condition table with the new field and build some conversion program to load the conditions from the old table into the new table, including the new field