Currently, XAF Security doesn't support shared parts when working with Domain Components and it is difficult to improve it shortly. We need some time to investigate this situation, find a solution and implement it.
This is why I have duplicated this issue to the following ticket: Security - Support domain components in the new security system (Client-Side UI and Integrated modes). This issue will be fixed when we finish that ticket.
Please track it to be notified when its status is changed. Thanks for your patience.