Contact manager with folders

Hello,

thanks to PortableApps.com, in the last year I've moved my digital life from a couple of computers to a single pen drive.

Unfortunately, I'm still struggling to find a good portable solution for my contacts.

I've been using Outlook for many years and in the last months I've moved ToDo(s) and Calendars to a portable application.

But I cannot find an application that can import my contacts.

I've read this thread
https://portableapps.com/node/4240
where Thunderbird is suggested.

I'm now using Portable Thunderbird (thanks john!) as my email client, and it was also able to import my contacts from my .pst file.
Unfortunately, Thunderbird address book does not support a folder tree organization: it has created an address book for every single subfolder in my (pretty complex) .pst file

Thus Thunderbird ends up having dozens of address books, in a flat organization.

Can anybody suggest a contact manager that supports hierarchical subfolders and that can import my contacts from a .pst file?

Thanks in advance for your help.