Showing inbox subfolders in apple mail

My question is how to add them to underneath the account they belong to under "inbox". I have several there already so somehow it's possible, I just can't figure out how to do it. Below is a screen shot of my current inbox with two accounts and several subfolders.

Quick update: I seem to be able to add these subfolders that appear under the mailbox by adding them using Outlook (the application, not the web-app).

While I prefer apple mail, this is a reasonable workaround... I can add them in outlook and use them in Mail.

The individual accounts show up first under "inbox", but under those are the subfolders. It is in that section that I'd like the folders to appear. I was able to create those in the past but am not sure how to create them now. I'm not sure what the change is, but perhaps it was when I updated to High Sierra... but I'm not sure.

I use my inbox as my 'to do' list. Once it's dealt with it's moved to whatever folder it belongs in. I used to be one of the people with thousands of emails piling up in the inbox... don't know how I lived that way.

So I can definitely see there isn't an apparent way to create these types of subfolders... but clearly they are somehow able to be created (as i already have several). One interesting thing is if i create a sub folder within one of the sub-folders under my inbox, that new sub subfolder is created correctly and appears in the correct place.

Even though I'm probably not going to find a way to create these folders as i hope, I am still really curious to know what changed; how I was able to create them before but cannot now.

Thanks for the reply.

When I add mailboxes in this way they do not show up under the the account in the inbox, but on the bottom of the sidebar (underneath the drafts/sent/junk/trash/etc.).