Here is a 90 minute workout I used a year ago during early base:
WKO5 is being used for graphing, but there are other tools out there like TrainingPeaks and Intervals.icu.
Here is a 2 hour segment from an outdoor ride at tempo (78% FTP):
see how the HR trend line and power trend line are parallel like a set of railroad tracks? That is 0.05% decoupling, essentially no decoupling.
And here is a 2.5 hour / 4500 foot (1370m) climb where I rode to HR (~154bpm) and let power drop as elevation went from 1350’ to 5850’
decoupling is about 7.5% and you can see the power trend line is falling while the HR trend line is almost flat.
Hope those examples help.