You could store decimal piece in an additional attribute (integer would be fine) for the UI. When you display the original decimal you format so it does not show the decimal. Next to it on the page you show the decimal attribute with a smaller size and vertically aligned to the top. I cannot think of any way natively from studio or any hacky CSS way to do this with a single decimal attribute.
I could get my decimals smaller as follows:
In the modeler I use 2 text widgets as follows:
My formulas are as follows:
I also added the following styling to the second text widget: text-small
EDIT: The ‘round’ function should be replaced with the ‘floor’ function
Hope it helps!