Where did the rest of my sims go? I only see about 10 at a time when I am selecting which to play
The "Select SIM to Edit..." and "Select SIM to Play..." screens show you a list of your sims that will fit in the display window, which depends on the screen resolution and size. On Windows and Mac, where you can change the size of the window, enlarging the window will only make the list bigger, not show you more entries.
On all platforms, even Windows and Mac, the list operates in a 'touch' mode, so to see all your sims, you simply need to click and drag downwards.