@widgetc I think you are looking in the wrong place, you need to look at your promoted listing "campaigns".
That is where you can mass change them (I set them all to be the same rate within a given campaign, when femme pointed out ones below 2% weren't being shown I went and looked and found a small number at 1% still which I did fix manually individually).
I find the tools better on .COM, assuming you're doing it from .CA to get there one has to:
.CA
-go to markdown manager
-click on advertising dashboard
-click on whatever campaigns needing updating
.COM
-go to promoted listings
-click on campaigns needing updating