XF 1.4 Get Miscellaneous Field Values?

What is the variable to get the values of the Miscellaneous field (Use this box to enter any additional CSS you would like to include) in CSS?

I tried
but it doesn't work.
In the Page Width Controller property, I have added some CSS in the Miscellaneous field, i.e. max-width : xxx, etc.

I just need to get the values I entered in the Miscellaneous field because I'll apply it to another element.

I can't use:
.myElement {
    @property "pageWidth";
    @property "/pageWidth";
because I don't need the other pageWith CSS (margin,padding,width,height) to be included.