How can I remove an external directory from the Portal?

Question

I did some consulting for a company a few years ago. Their Azure directory appears in my Azure "Portal Settings". I can't access anything in it, and I don't have credentials for it anymore. It's in the way. For example, if I do an az login, I get a warning about "The following tenants don't contain accessible subscriptions." I'm forever afraid that I'll accidentally select it when I mean to work with my own directory. I trip over it all the time.

But I can't find a way to remove it from my portal.

If I get to the "Classic Directory" overview and use "Manage tenants", I see my own organization and the other org. If I try to delete the other org, I get a message that I don't have privileges. (Which makes sense, as I don't want to delete that org, I just want to disassociate from it.) If I click "Leave", I'm prompted for credentials and the credentials from my home account don't work.

How can I leave the foreign directory? At least, how can I remove it from my prompts and my portal?