Using case logs as evidence of competency has been of concern to educational leads on the College portfolio for some time.
The case log function was always intended as an online version of a log book. It allows you to keep notes for the cases you see, demonstrating you have seen a good mix of patients and complexities. However, this can only demonstrate quantity.
You can create a followup to a Case Log, and then subsequently map this to the competencies this evidence demonstrates. Mapping a followup to a competency can be done in the same way as mapping an activity to a competency.