Allow width adjustment by pixel value with a numeric stepper

Currently, the snapping width can only be adjusted by percentage. It would be helpful to also allow adjustment by exact pixel values.

As a further improvement, consider adding an input box with a numeric stepper. Adjusting a precise value using a slider is painful, so this would make it much easier.

It would be great if this UI improvement could be applied globally for consistency.

I think you currently can click the numbers and type directly.

I do have plans to do a complete refresh on the window snapping and snap area UI this summer, then this will change anyways!

Some parts of the UI can, but this one doesn't.