You can split stereo tracks into left/right or mid/side mono tracks. This is a virtual split which does not affect or create audio files.
Procedure
In the Audio Montage window, right-click the track control area of the track that you want to split and select Split into Left/Right Mono Tracks.
Result
The track is split. If there are clips on the track, the two stereo sides are now separate clips, allowing you to move and edit independently.
The mono tracks are automatically grouped and can only be moved and resized together.