Although there are multiple video outputs on certain video extenders at StarTech.com, these do not create independent displays. Instead, the input to the video extenders with multiple outputs gets mirrored or duplicated. This is because video extenders have built-in video splitters to allow for multiple video outputs.
For more information about how mirroring works, refer to the following FAQ: https://www.startech.com/support/faqs/technical-support?topic=video#mirror-span-extend.
Note: The ST12MHDLAN can be used to create a video wall which allows for independent displays. For more information about the ST12MHDLAN, refer to the product page for ST12MDHLAN: ST12MHDLAN.