Data List Viewer Management

I’ve made a bunch of Data List Viewer formats. How do I clear the formats that I’ve created since they’re now all appearing in the design view drop down.

Also if I make one and want to edit it how do I do that? So far I’ve just kept them in separate screens but that seems like it’s not how it’s supposed to work?

Note that currently only PRO account can edit the custom layouts however the development team are working in a fix.