HQ users can create mapped values for segments in HQ and link them to corresponding segments in child accounts. This will streamline the process of syncing automations by eliminating the need to update each child account individually.
Segment mapping is available only for conditions mapping in automations, with support for selecting segments in pushed corporate emails coming in a future update.
This is not the ability to create a segment in HQ and sync the segment to child accounts.
Go to the Cogwheel in the top right corner of the screen > Settings > navigate to Mapped Values > Segments.
Then, map the segment accordingly.