In Motion, group the elements you reuse over and over, name the group something meaningful and then go into the Inspector > Library and select Favorites. Drag the group from the layers list into the Favorites view pane. You will always have access to those pieces from Favorites.
In FCPX, make a compound clip from the segments you want to save. That very act will save a copy of those "grouped" clips into an Event of your choosing. You might want to create a specific Event to hold the segments you need easy access to.