I see, so this question is not specific to the WYSIWYG field? That is where your question became confusing.
I would create a layout in your flexible content field called page_break.
Then in your template, within the flexible content loop, create a counter variable which starts at 1 and gets increased each time the page_break layout is used.
Then, you can look at the $_GET param “page” and match it to your counter variable value. If the value does not match, use a ‘continue’ statement to ignore the current loop’s layout.
Therefore, if you had &page=2 in your URL, your loop would only show layouts which appear after the first ‘page_break’ but before the second.
I hope that helps
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