Can't AB test an element in Google optimize?

Question

Google Analytics

Good time! Faced the impossibility of hanging AB test of one repeating element on all pages. That is, the element is present on all pages of the site, we change its CSS properties, for example, color, in addition (the addition to the browser with which editing is carried out), the substitution works on all pages, and after running the test, only on the main page and when going to any other page, we see the original option.
Yes, I also noticed that the preview of the modified version also works only on the main page when we go to the page without changes.