Mount vdi as drive in Windows

You'll want the 64 bit since your (host) OS is 64. The main thing is that Winmount will install drivers and you'll need the drivers to match your OS (64).

Try ImDisk it's saved my bacon a few times and it's free!

I was able to recover files from Ubuntu 18.04 guest on Windows 10 host (Virtualbox 6.0) as simply as opening the VDI file in 7-Zip by right-clicking the VDI file -> 7-Zip -> Open archive and drive contents was shown like any other archive.