Most manufacturers sell adapters so you can use a router or a jigsaw with their saw track, but DeWalt also sells two accessories for their track saws that can both help align the track and be used as a layout tool.
The first accessory is a T-square attachment. Clip it onto your track and you can align the track perpendicular to the edge, or use it as a rather cumbersome T-Square. The second accessory allows you to set the track at a preset angle. DeWalt doesn’t say what the angle range is, but it looks like it’s about -45º to 90º to 45º.
The T-square attachment will run you about $17, while the miter gauge attachment will run you somewhere in the neighborhood of $34.