A fairly recent change was introduced where selecting a DTL from within the Rule Editor presented the user with a button to open the Data Transformation Builder Editor (DTL Editor) which took the user straight to the DTL.
However, if you open a DTL and then wish to view a subtransform contained within the DTL, you are forced to manually search for the DTL of the subtransform using the standard search options.
A simple extension from the first change would be to update the Data Transformation Editor by adding a button to the Action Tab for the subtransform action.
Thank you for submitting the idea. The status has been changed to "Future consideration".
Stay tuned!