Safari on iPhone and iPad has a hidden feature that lets you bookmark all open sites in a single folder. To keep things as you left them, quickly add bookmarks to all tabs in Safari using this trick.
Open the "Safari" application on your iPhone or iPad, then tap the URL bar. Here, enter an address URL and then press the "Go" button on your keyboard to open the site. Repeat this procedure to open all the sites to which you want to add a common bookmark.
If you already have the sites open, click the "Tabs" button and close any website to which you do not want to add a bookmark.
Then press and hold the "Bookmarks" button, then select "Add Bookmarks For X Tabs".
After selecting the folder, click the "Save" button.
Safari has now saved all your open tabs. To access the tabs later, press the Bookmarks button from tool bar of Safari.
Click the "Open In New Tabs" button to reopen all tabs. Later, you can click the "Delete" button here to delete the folder.
From the folder, you can also swipe left on a specific webpage and then click "Delete" to delete the bookmark.
Source of information: howtogeek.com