1. Use the 'search-in-clips' feature while playing back a clip.
Excerpt from the Help PDF:
Click the magnifying glass icon, then configure the 'Find in clips' dialog something like this:
I've struggled getting this work satisfactorily in the past, so YMMV.
For example, Ken has told me that “the search and testing features will use the camera's current motion settings. Maybe we need to add an option to the search page to select the profile?” I replied with "Yes, please", but he has yet to make the change. Maybe more requests will help. [EDIT - Fixed in 5.6.2.1; see next post.
2. Less useful is creating alerts manually by exporting a portion of clip with motion to the Clipboard, then moving it to the Alerts folder.