Thanks for your reply.
I actually did go ahead and use the trusted proxies section, so that millions of Cloudflare IPs would be ignored in the “X-Forwarded-For” header.

The trusted proxies option allows CIDR, so that a single CIDR range (104.16.0.0/12) that covers 1 million+ IPs can easily be handled. (But I see that doing so may not be necessary, because the IP in that header is the visitor IP, not Cloudflare’s IP. It would only potentially be necessary if the IP in that header is Cloudflare’s IP.)
Here is the image of the section that you requested:

Re: my other question:
I was primarily referring to syntax, for being able to input all of Cloudflare’s IPs in the WF option “Whitelisted IP addresses that bypass all rules.”
It would not be feasible to input Cloudflare’s IPs in that section, unless this works:
104.[16-31].[0-255].[0-255]
If that ^^ does not work in WF, then you would have to do this:
104.16.0.[0-255]
..etc
..etc
104.16.255.[0-255]
104.17.0.[0-255]
..etc
..etc
104.17.255.[0-255]
..etc
..etc
..which is not feasible for the average person to input. It would be 4096 lines.

So, all this started with wondering how to get Cloudflare’s IPs input to the WF option “Whitelisted IP addresses that bypass all rules.”
I saw that WF does allow that type of grouping of range brackets in IPv6, in order to identify larger ranges, so if WF also allows grouping of range brackets for IPv4, i.e., 104.[16-31].[0-255].[0-255], then it would be possible to get all of Cloudflare’s IP addresses into “Whitelisted IP addresses that bypass all rules”?

Summary:
This quest initially started with simply wanting to whitelist Cloudflare’s IPs. Then, I saw that there might be a syntax problem with getting millions of Cloudflare’s IPs input into the WF whitelist option. After that, I saw that I could use Cloudflare’s CIDR range in trusted proxies, but it appears that it’s not needed there, because the “X-Forwarded-For” header is using the visitor’s IP, not Cloudflare’s IP.