This is what I used to generate the first report. As I mentioned, I find it's a lot of work to add in all the custom fields in order to create the report that I need, and I don't see an option to save all those fields so that I can reuse them. That's what I want, the "add a bunch of custom fields and reuse them later" functionality. I don't see instructions on how to do that on this page.
These seem to describe the "old version" of reports, that use a completely different UI than the page at /mnt/overlay/dam/gui/content/reports/createreportwizard.html
I might be able to go down this path, but before I do, I'd like confirmation that these reports and the reports from the first link are separate. Are they? And is there no way to create (and save) a custom report in the style of the reports from the first link?
I'm in a similar situation where I need to regularly retrieve asset reports with quite a few custom metadata values, which is tedious to build every time. It may be more work to setup, but ACS Commons has a Report Builder that looks like it allows for quite a bit of customization. Most importantly, the report configuration persists and can be executed at the click of a button. I haven't explored this fully, but it sounds like this could be a possible solution. Report Builder