You can direct select elements by holding CMD when clicking on items that are part of groups. Marquee selecting anchor points is landing very soon, so that you could select parts of your rectangle. Do you expect a different behavior? Did I understand your request right? Thanks for your feedback.
An error occurred while saving the commentStefanija Naskova commented
This is one of the most annoying things in XD at the moment.
7,700 votes411 comments · Adobe XD: Feature Requests » 02 : Prototype mode · Flag idea as inappropriate… · Admin →
Reopening the feature request, based on feedback.