1. Navigate to the ApplySimple function in Developer by opening the Schema Objects folder -> Functions and Operators -> Functions -> Internal

2. Right click on the ApplySimple function and click “Search for Dependents”.

3. You will then be shown all of the objects using the ApplySimple function. You can narrow these objects down to a specific type by selecting the Object Types tab and clicking Find Now.

This workflow can be used to find objects using other functions as well.
KB442503