The Tracks page in the sidebar is your local track database — AiM's full track list, plus anything you've imported or copied off a device. Sessions are matched to tracks from here, and sector divisions are drawn here.
Tracks are grouped by country and searchable by name. Selecting one shows a satellite map of its shape and, alongside it:
.tkk or Race Studio .ztracks files in from disk.Added in 1.5.0. If a venue isn't in AiM's database — a new circuit, a private test track, an autocross course laid out in a car park — you can build it, in AiM's own .tkk format. It's a real track like any other: it can be sent to a logger, and Race Studio reads it.

Building a track from one lap of a session
Hit New Track on the Tracks page. The shape can come from either:
.kml, .kmb, .gpx, an existing .tkk, or any session format AimMac reads.Then fill in the rest: