HubSpot should allow marketers to define targeting filters directly within a marketing email, creating a temporary audience that exists only for that send, rather than requiring a saved segment.
Most of our marketing emails are sent to one-off audiences (for example, contacts who downloaded any of several specific publications). Today, this requires creating segments that are used once and then have to be identified as temporary.
Supporting temporary, email-specific audience filters—alongside the existing option to select a saved segment—would reduce segment clutter and eliminate the need to create, name, track, and later delete single-use segments.