To clarify, as an example, you have video on track 1, audio on track two and you want to "ungroup" them so you can move the video or audio object independently?
If that is the case, click the pair so they're highlighted, then click the Ungroup icon (weird chain with small arrows pointing at it) or do Shift G.
You can test the ungrouping by clicking on one or the other; only it will be highlighted.