There are times where I would like to store confidential information that should be treated like a password (with visibility constraints and auditing capability). Some examples are 2FA recovery keys and certificate storage.
The 2FA keys can come in all shapes and sizes, but essentially a multi-line text box (not rich text) will do the job just fine.
Certificates are a little more complicated, but I don't think anyone needs to actually store web server certificates, just data in certificate format. For instance, SSH private keys would be a good candidate. There are also several applications and services that use a certificate format to store some kind of recovery data (like drive encryption or backup applications). There are other applications for this as well, but like before a simple multi-line text box (not rich text) will handle this just fine.
One important aspect here is that certificates are often generated from either Windows or Linux, and depending on where it's generated the line ending encoding is different. So the multi-line textbox would need to preserve whatever line ending format and character encoding that was supplied.