Dynamic group membership change is not shown in VST in Identity Manager.
Currently if user is created or modified which would caused them to be added or removed to Dynamic Group there is no event or task in VST that would indicate this.
To be clear the task/event of creation or modification of user is visible in VST, only change in membership to dynamic group is not visible.
Identity Manager 14.5, 15
Product design.
Currently IM does not show changes to membership of dynamic groups in VST as part of event or tasks.
We encourage customers interested in this feature to create an enhancement request so this might be implemented as functionality in future releases.
Instruction how to create enhancement request you can find under this link.
If enhancement request already exist please upvote it to make it more visible for Product Manager.