The rendering of the list of values for a parameterized lookup is not supported until 15.7. However, in 15.4 and 15.4.1: If the user selects and saves a value from the lookup in Classic, that saved value appears in the column cell for that record in the New User Experience (UX). Additionally, a user can define a parameterized lookup in a studio object and provide an API Alias. Unexpectedly - This will cause the field to appear in any of the New UX grids column panels.
Steps to Reproduce:
New User Experience (UX)
Clarity 15.4 and 15.4.1
Remove the API Alias from the attribute, then it will not show in the new UX.
The API Attribute ID has been deleted preventing this attribute from showing incorrectly in the New UX
Parameterized lookups are now supported, so the API Attribute ID is automatically populated for the respective attributes such as Project Category
See also: Lookups master KB for Clarity