There are some really excellent page shape dividers here.
If using the code generated using https://shapedividers.com. Edit the code with a text editor and select just the SVG part we want and then copy the SVG code. The part of the code to copy is everything from <svg> ... </svg> including the <svg> ... </svg> part. i.e, it must start with <svg> and end with </svg>.
If it doesn’t work when pasted into an SVG stack then either the colour set in the SVG stack matches the BG of the Container, so you can’t see it, or you didn’t copy the full SVG code correctly. Recheck the instructions above and try again.