Cant select custom properties for user parameters in dimension editor

[Des_Seals]

I have a drawing that im trying to insert a user parameter as a fraction to an existing dimension. I know with leader text i can select the property settings above the component properties and those let me use the formatting that i set in my part or model. When i try the same thing with a dimension the type property settings are always grayed out. Is there a way to add a user parameter as a fraction to a dimension?

kelly.young has embedded your images for clarity.

[johnsonshiue]

Hi! Could you share the files here? There should be a logical reason to explaining the behavior.

Many thanks!