OneDrive Personal Vault is limited to 3 files for anyone with a free OneDrive account. It’s very easy to bypass that limitation, store as many files as you like and even add another security layer.
There are several ways to store multiple files inside a single files. Use one of those file types to store all your Personal Vault needs in a single file.
ZIP files – the widely supported compression standard. Supported in Windows.
RAR – RAR is similar to ZIP but with some better options including ‘Solid’.
DOCX – Beating Bots, Spies and Cock-ups show how to use Word as a storage container for any type of file or photo.
The three files can be any size up to the100GB (OneDrive maximum single file size is 100GB except for work/school accounts at 15GB).
All three file types have a password protection option. If you wanted yet another layer of security, add a password necessary to open the ZIP, RAR or DOCX file. This is probably an excessive option when there’s already two layers of security in Personal Vault but it’s worth keeping in mind.