16. The system of claim 15 , wherein the layer axis is collapsible such that at least one canvas layer does not have a layer coordinate that appears in the digital timeline, and the layer coordinates of the timeline objects that are linked to canvas objects present in a current view of the digital canvas appear in the digital timeline.
15. The system of claim 12 , wherein: the digital timeline further comprises a layer axis; and the positions of at least two timeline objects in the plurality of timeline objects have different first and second time coordinates along the time axis and a same layer coordinate along the layer axis, such that the two canvas objects linked to the two timeline objects appear in the digital canvas at different times and in the same canvas layer, and wherein the layer axis corresponds to a front to back ordering of the plurality of canvas layers in the digital canvas.