Back 20+ years ago I used alternate data streams to his my collection of files (the ones you find online as a teenager) behind a text file. You can shove anything you want (I think) in them, even including extensions to make sure it opened in the right program (i.e. test.txt:malware.msi).

It works, and yes only on NTFS… but many applications may not be able to open these “files”.

It’s actually sort of a weird historical thing, goes back to the roots of Windows NT in VMS and also compatibility with Mac OS (classic) and its “resource forks”