A list of common Tifinagh abbreviations / ligatures, taken from Grammaire, Dialogues et Dictionnaire Touaregs by A. de Motylinski. The characters in the left-most column represent the combination of the characters in the middle and right-most columns.
The full text of de Motylinski's booklet is available courtesy of  Andries Brouwer's page at Eindhoven University of Technology.