In the current (2019) version of Lightroom Classic, you cannot sync a smart collection with Lightroom Mobile. This is unfortunate because I use many smart collections to organize my photographs. In this video, I present a workaround to help overcome this issue. To make this work, I make two smart collections that show whether or not photos should be added or removed from a synced collection. Using these two smart collections as a guide, I add or remove photos to the synced collection.