I've created a new rendering and have set the Datasource Location and Datasource Template. However when I add it to a placeholder inside the EXM Experience Editor I only see the option to select Existing Content - I cannot create a new content item.
What have I missed setting such that I can add a new content block into my email with a datasource item created?
Using Sitecore 9.1.1.
Update: Have reproduced this in a vanilla instance of Sitecore 9.1.1 and SXA 1.8.1 using the sample newsletter template.