You go to the posts tab, there you will see below each post (see the screenshot below) a little graph called engagement evolution’ This graph shows you how fast the number of reactions and comments went up.
If the slope of the graph is beyond a certain value and some other conditions are met, then the probability that a post is boosted is very high.
I’d say we’re 90% with that feature - only need some right machine learning model to train over some known data and run it.
At the moment you have to apply your judgement - if in the timeframe the engagement of the post skyrocketed and it doesn’t seem to viral, and the page is a business page, not some entertainment one then > 90% the post is boosted.
For a new page, wait 2 or 3 days to collect data, and then you’ll be able to see the engagement evolution of each post.