In some cases, clients may find that they have an event where it would be beneficial if the registration fee was split into two separate designations. For example, If someone has an event where the registration fee is $1,500, and would like $1,000 to be non-charitable and go to one designation, and another $500 to be charitable and go to another designation. 

Currently, the application will allow you to configure the event registration with an option for an additional donation, however, this can be confusing to the constituents and does not automatically map the additional donation to a specified designation. I could see this being a major need for clients in the near future and think this would make for a great feature in an upcoming release.