In C++, a replicated property's RepNotify function can include a parameter that represents the property's value before the new replicated value was applied. In blueprints, RepNotify functions are not editable and are checked to make sure they have no parameters, so this parameter cannot be added.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-109941 in the post.
|Component||UE - Gameplay - Blueprint|
|Created||Mar 4, 2021|
|Updated||Jan 28, 2022|