@MeganWhiteBV Does this help you?

https://www.qualtrics.com/support/iq-directory/lists-tab/creating-mailing-list-samples/

Unfortunately no, this only allows you to create a sample from a “list”, whereas I’m working with a segment. There doesn’t appear to be any way to make a segment into a list. 

@MeganWhiteBV You are right. Actually I do not see some functionality that could be used for this. As I think that there is also no export option for segments, you can also not export and upload a manually reduced list as mailing list. 

The only thing you could try is to use any of the contact, embedded and transactional data which is independent of your actual purpose/segmentation to try reducing the list without building a sub-group that does not anymore represent your original idea. 

Maybe someone else has an idea.

Best
Christian