It seems version alefragnani.Bookmarks-10.2.1 will show the error command 'bookmarks.toggle' not found when I install it on a clean vscode installation.
After deleting the install, followed by installing alefragnani.Bookmarks-10.2.0.vsix the extension seems to work as expected, after which I can upgrade it to 10.2.1 .
My operating system: macos, however I'm able to replicate the exact behaviour on a clean windows VM on Azure with only vscode installed using ninite. Also on this windows machine manually installing 10.2.0, uninstalling and then installing 10.2.1 the usual way makes it work again.
Debug output:

Confirmed:
command 'bookmarks.toggle' not found error occurred to me too.macOS
VS Code 1.30.2 (1.30.2)
I can confirm that 馃槥 .
I'll fix it ASAP. I hope a new release later today.
Thanks for reporting
Aaand, it's back.
@YuryTheName it's not the same _root cause_, and is already reported in #395.
Most helpful comment
Aaand, it's back.