How can I skip the login page to create an A/B test if it opens in another window?

Hi all,

I have detected another issue regarding the log in.
Now I need to activate an A/B test on some pages that their login page opens in another window. I have tried the same process I learned here, switch to "browse" mode and then enter the desired test page. Once there switch back to "compose" mode. But it doesn't work.

Can anyone help me?

Thanks in advance,