What is the fastest way to use subscript in google docs for science reports?

[Hanuman]

I am also doing a chemistry laboratory report and I have to write a lot of chemical equations such as H 2 O and CO 2. Having to go through the Format menu each time that I have to use a subscript is extremely boring and is really slowing down the workflow. I have attempted to find a quick toggle button on the main toolbar, however, I do not see it. Does anyone know a specific keyboard shortcut for subscript in google docs that works on both Windows and Mac? Another question is that how can I highlight an entire list of numbers and change them to subscripts as a whole or do I need to do it individually? It would be a savior to receive some suggestions on how to make this process even more efficient!