When [Shared BETA] is selected, your listing will appear in the New Search BETA search results in accordance with the Phase 3 New Sharing Rules.
There are individual [Shared BETA] tickboxes under:
For Rent - Long Term
For Rent - Short Term
This allows you to independently share the property for sale and not share for rent, or vice versa.
What is the difference between Search 1.0 and Search 2.0 Beta?
What is the difference between the Shared and Shared BETA tickboxes?
Search 2.0 Beta - results page explained
Q&A - New Search 2.0 Beta