Can you plug in a graphics tablet and use it as a mouse for your smartphone with a usb-to-phone adapter?

No, you typically cannot use a graphics tablet as a mouse for a smartphone, even with a USB-to-phone adapter. Graphics tablets require specific drivers and software to function properly, which smartphones do not support. Additionally, most tablets are designed to work with computers rather than mobile devices. For smartphone interaction, you would need a compatible touchscreen stylus or a dedicated mobile mouse.