Trouble adding new values in smart lists

Hello, I am trying to figure out what devices/platforms/browsers people are using to open our emails. I'm using smart lists like so:

When I expand the platform selection to add options (such as Windows 10) the options that I am looking for does not exist in the system.

I am restricted to only what is provided in the box to the left.

How can I add additional value options?

Thank you in advance!