It's really easy to create your own Song Collections with Yousician. Just find the song you want to add from Songs tab, click to see more options and choose Add to collection.
The option to add songs to a collection is also available from the song start and end screens.
Once you open the menu, you can add the song to a collection and then choose to either add it to an existing one or create a new collection.
You will find all your collections under the Songs tab by clicking My Repertoire.