The standalone version is different from the plugin. There are no adjustments at the top of the Scaler 3 window in the plugin and in both versions, the ‘targetting’ on the bottom corners is very finnicky; if you have a smaller monitor (I’m using a 22-inch monitor and I struggle), you have to get the mouse pointer in a very small region of the corners to have the pointer become a double-headed arrow.
If you can’t get it, you can set ‘Mouse Arrows’ in the ‘Accessibility’ area of Windows which allows you to move the mouse pointer with the arrow keys - I don’t think there’s a toggling keystroke to enable/disable it, though.