Got and understand Dropdown selection (in concept anyway, haven't put that to the test yet).
On the other question, I believe I didn't include enough information to obtain the answer I expect.
Currently the Custom Category is setup to include one planet with the three snippets correctly. Currently, the way I would add information is update the one planet I have been given, and then would click to add another snippet for Name, Description, Image three times to get the required fields.
I'm wondering, if its possible to call this for example "Planets Full Description" and when you choose to add one of these, it adds all three snippet types.