Resolution:
When using the 004010UCS guideline, BusinessConnect throws a validation error at the group level because the GS08 code value "004010UCS" does not exist in the code list, as shown here:

BC Error message:
Group Validation Error

Context:  Segment-GS | Element-480
Location:  Segment:2 | Element:8
Category:  Rejecting
Severity:  Normal
Details:  Code Value "004010UCS" not found in the dictionary code list for GS08 (D.E. 480) at col. 50
ID:  10605


To resolve the issue, do the following:

1). Open EDISIM Application Manager.
2). Click on Standards Editor.
3). In the Standards Editor, go to File > New > User Gudelines (or ther tab)> select "4010UCS" > Click on "Next" .
4). Select the required Transaction Set. For example, "880 Grocery Products Invoice" > Click on "Open" .
5). Go to the Dictionary Objects > Segments > GS > 08 > select "Code Values" tab (lower bottom).
6). In the lower bottom menu, click on the "L" icon to add a new code value such as 004010UCS.

You can follow the above steps for interchange, group or transaction elements to add code values in the code list.

How to add custom code values in the code lists of Interchange and Group header in a sef file?

TIBCO Foresight Standards Editor documentation