create a second, separate iCloud email account

I think you are asking if you can have two primary iCloud.com email addresses using the same Apple Account.

You cannot.

Create a primary email address for iCloud Mail - Apple Support

If you go to Settings > Apps > Mail > Mail Accounts > Add Account > iCloud, here’s the result.

Perhaps Hide My Email is what you’re looking for.

How to use Hide My Email with iCloud+ on your iPhone or iPad - Apple Support

You told us how you’re trying to solve some issue. We can very likely assist better if you tell us what issue you’re trying to solve.

Womac23 wrote:

Hello Sberman,

I want to create a new email address to use for all my banking and investments. Currently I have two email addresses and folders icloud and BT as you can see in the screengrab. I want a 3rd email address and folder so that only banking and investment emails go into the new 3rd folder? Hopefully this makes more sense. Thank you for your patience.

Well, you don’t need even that.

You can create a rule on your Mac that can sort messages into specific purpose-created mail folders.

Rules I’ve created sort all sorts of mail as it arrives, as some arriving mail I don’t ever need to read but do need to retain, and some I can just delete.

Use rules to manage emails you receive in Mail on Mac - Apple Support

You can certainly also set up aliases or hide-my-email addresses and such, and can set up completely separate mail accounts if you really want, but I suspect creating and using mail rules will be both better suited, and less work.

Womac23 wrote:

Hello,

On my Mac I have the Apple email software. I have 1 icloud email and one 3rd party provider email for example @gmail. I send and receive emails from my icloud account and these are completely separate from my gmail account. I could for example create another 3rd party account such as Yahoo and then add this account to my Apple email. But why not a completely separate icloud email for example XYZ@Noticloud and have the mails to and from this account in a completely separate account / folder. iCloud aliases don't work so can I set up another separate email account in Apple or am I restricted to only have 1 icloud email account

Mail already works that way.

Apple Mail offers a combined inbox yes, but immediately below that you can select each of the configured mail accounts.

Configured with an Apple iCloud address, and a Gmail address, you will have the combined Inbox (which shows both inboxes), and two completely separate inboxes for those messages on the iCloud server, and those messages on the Gmail server.

It’s good we can now understand what you’re trying to do. As MrHoffman and I both explained above, you cannot have two primary iCloud email addresses. Personally I use three primary addresses each with a different email service provider (one of which is an iCloud.com address). Hope that helps.

Glad you found our advice helpful.

Enjoy your Apple gear.