In Safari I've logged into a website and need to open a second tab. I want to look at a different page on the website without clicking away from the page I'm on.
You can bookmark or make a bookmarklet for the first tab. Then log in a second tab and go do your thing. Then to return to the first, open the bookmark or tap on the bookmarklet. It should take you to where you were.
Generally it's a little plus icon top right hand of the current tab your on, just click on it and it should open,and also in options you have to have it set to enable tab function.