How do I view all my weight data in apple health on iOS?
On the weight screen it will show a graph with D, W, M, Y across the top to change the graph time scale for days, weeks, months and years. While you are on this same screen, scroll all the way down to the bottom and there will be a button that says Show All Data. Click on this button and you can view all the records you have entered and also edit them. This applies to iOS 13.6.1.
Posting this answer because my version of Apple Health did not have a health data tab that @anki mentioned in their answer.