Is there a way to ensure that certain investors only see certain offerings in the MaaS Marketplace?

The User Groups feature allows you to choose which users can see your Offering(s) if you do not want them to be public. 

The User Groups feature allows you to choose which users can see your Offering(s) if you do not want them to be public. 

Once you've created a User Group, you can then Edit Offering and place your Offering in a User Group, so that only certain users can see that Offering. Please note that you will have to manually place each User into a User Group. You can do this by navigating to the Users page and clicking the pen icon to Edit the User, and then checking the Group you would like to place them in.