This is pretty tricky, unfortunately. When you preview a segment it shows the leads in that segment IF it were just a normal Smart List. The preview doesn't actually do all the work to exclude other segments.
Because of that, default isn't going to be terribly interesting. However, maybe with some of the performance work we're doing this might be possible in the future.
Thanks Erik! I may have miscommunicated, so let me clarify just in case!
I'd like to see leads in the Default segment because I might find leads that should fit in segments (but filters aren't capturing them). If I wanted to make sure that my segments have good coverage of the database, I need to find the leads that aren't currently in a segment.
If there are 3 segments A, B, and C, then a Default, I could imagine the Default preview would be a smart list of "Not member of smart list of segment A, B, or C". The workaround here is to create a smart list of the filters in segment A, B, or C before approving the segmentation. Then I'd find the rest of the population that would qualify to be part of the Default.
Yeah, we didn't do that in the initial design because we felt there was a fairly high chance of that being very slow. Now, as things get faster I bet we can at some point.
.png)