custom side bar pixel, how do it?

[LoveStream]

Hello, team and good coder.

In the create new Grid, how could I select my own size?
Unfortunately there is just a few sample size so I can't use other one that I want to.

If coder may add custom input box for integer(numbers) enables, I were create my own size of Golden Ratio colum. Isn't it?

If anyone knows how to customize, please let me know.

Thanks in advanced.