By "transformer" are you talking about a layout which has overlapping or adjacent coils, such as those for an inductor? Could you use an inductor as a starting point for this? There is Solution 1809475 on SourceLink for a Spiral Inductor.
Oh, while I was looking at that Solution, I noticed that it points to examples in the software hierarchy, and I see that there is a transformer PCell there:
Hope this helps you!