The great Polish film director Kieslowski was famous for including certain scenes in multiple films. Perhaps this is because he used the same characters, or borrowed footage of certain scenes shot from multiple angles for different films and narratives. Whatever the artistic impetus, and whatever the process techniques that made this sort of magic trick doable, the effect for the attentive film-goer, especially watching multiple films over a period of time, was a kind of Cubist re-arrangement of time’s flow, causality and teleology, fate, destiny and recurrence.
You can use this technique in your songwriting work.
You can reference your other works. Not in ways requiring the auditor to go off in search of the reference to complete their experience, but as a way of weaving your work into a larger texture, tapestry. Create sequels, circles, rings, cycles. This can be approached as a learning and skill development technique, an artistic practice, and also as a kind of marketing strategy—a way of creating a narrative around the body of your work for your audience. Give someone a great first experience, then some threads to follow.
I like to say you can steal from yourself with impunity—as long as you agree in advance not to take yourself to court.