Re: OneNote Page Items into Individual Planner Tasks
The closest I've got is this: https://willpage.dev/2020/08/21/extract-from-address-from-forwarded-email-in-power-automate-logic-apps/
The principle is the same, except in this example we're extracting details from an HTML email body, but you can use the same technique for the HTML text from OneNote. Something to note though: I wrote that article before the slice() function was a thing, and slice() is far easier to get a slice of text using the start index and end index than using substring() with all those nested calculations.
But in your scenario you might be better of with another technique:
Split the text with split(<text>, '<li>') where <text> is the dynamic output from your Get page content action from OneNote. That'll leave you with an array of string items.
1. Bullet points in HTML:

2. Split on <li>


Now add a Filter array action and filter the previous action for item() contains </li> and the result will be the list items.


Now do a Select action and switch to JSON mode, which is the little T icon on the right and put the expression
substring(item(),0, indexOf(item(),'</li>'))
in there, which should strip out the closing li tag and anything after it.


The output of that is an array you can use in an Apply to each to create your planner tasks.