No, there isn't... Ohhh, so many dum dums will not understand your question and will offer advise on how to slide the sidebar back... but they have zero idea of what we speak. Why apple forces me to engage with unnecessary clicks to reclaim my precious screen space flys in the face of what I most liked about MacOS. If I couldn't participate in apple's hostile take-over of 20% of the desktop I paid for, can't they offer to sell me my iMac for 20% off? It really really ticks me off.