Thats fairly easy and beauty of Appsheet.
I suppose you currently set the ref type column and reference table is set to Category in Products columns.
Assuming that, change the column type to Enumlist. Then for valid If constrain, please place select expression
Select Expression Example.
Select(Category[key column], true)
This expression simply return the key column out of the category table. If you want to get the certain set of the rows from category table, then add the conditions by replacing true.
[Key column] can be other column depending on what sort of column you have in your table. For instance, if you want to get the dropdown list for multiple selection referring to the column name, such as “Category Name” then formula to be
Select(Category[Category Name], true)
if you have other column for instance, the sub category in category table, then you can add condition like
Select(Category[Category Name], [Sub-category]=“Office”)
Something like that.
I dont intent to make the simple story complicated, but you can add the initial value for Enumlist as well.
For the initial values, set the formula like this
LIST(“TBA category name1”," TBA category name2", “TBA category name3”)
This return the list of category as you selected, and when the user open the new form , the value is set as selected when they see the dropdown.
Hope this makes sense.