This mockup describes a UI for a trait to select one or more segments from the set of defined segments in the Segments app. It only allows to pick segments, not to search for them, but this is not mandatory, actually: if the control is easily capable of auto-suggesting matches for segment names typed into one of its input fields, feel free to offer this. You should then model the search part after the trait UI for selecting locations.

This mockup does NOT use our basic rule builder: it assumes that its values are always "OR" connected (hence the term "any of" next to the field's label). When a rule builder is available used, just replace that label with a combobox offering "any" (OR) or "all" (AND) to concatenate terms (see visual design example attach here as well).

The UI of a trait is largely depending on the trait itself, but it also has some aspects it shares with other traits. The UI described here acts as a good example of a trait supporting multiple values, but only offers to pick, not search for them - other traits with the same requirement should be modeled after it.