Ernie, I have an off-canvas menu on my sharing page, there are versions for RFF and SD3.x. Since I just made one page, I didn't create a symbol, but the element to select to create a component is also the one which should be made into a symbol.
Yes Ernie the Off Canvas content needs to be on each page. Wayan is saying make it a symbol on the first page you add it to. When you copy the page any changes made to one will be automatically made on the others.