Hi Sanoza,
Spy any topmost element of the webpage. This element should always be present on that webpage.
If this element is used in a Reader stage with an action called 'Get Screen Bounds' then it returns a collection with the columns as below-
View attachment 1542686732765.png
With every Activate & Scroll, the Top and Bottom property of the element changes (blue).
And you will notice that after it reaches the end of the page no matter how much you scroll these two properties remain the same (green).
View attachment 1542687581339.png
So what you need to do is have the Activate & Scroll followed by this Reader stage in a loop like structure.
The loop is a Decision stage where you check the
previous Top and Bottom values (stored in a Data Item in the previous iteration of the loop) and compare it with the
current Top and Bottom values. If they are the same then it means you have reached the end of page and your diagram should follow the 'Yes' branch of the Decision stage else it will continue to do the Activate & Scroll->Reader stage in a loop. Your action to capture the screenshot would be in the 'No' branch where the Decision stage checks [prev value] = [curr value]. Have default [prev value] may be as 0 so that it is used during the first iteration of the loop.
There could possibly be more such ways if you explore more on something like this.