Layers when using shapes and lines

Hello, this is probably a dumb question, but I am completely baffled.

I am a photographer and usually use PS for object removal and other corrections, so I'm not used to doing a lot of drawing.

I'm trying to create a PNG template with a table that I can use as a checklist on my Mobiscribe tablet. The problem I'm having is that each shape is created as a separate layer - and every time I add a new one (I'm using the rectangle and line tools), the others disappear. Clicking on the "eyeball" in the layers as I would do with a photo does not seem to work.

I was able to get multiple shapes on one layer by choosing "combine shapes" in the dropdown but then I am not able to modify or move the shapes individually.

How can I make all of the shape layers (and text layers, if I ever get that far) visible at once so I can export them into a single PNG file?