I haven't found a way to quickly do this without having to entirely disable the extension in the "Extensions" panel. In IntelliJ IDEA, one can easily toggle on/off the emulation with a configurable keyboard shortcut. I guess it should also be possible in VSCode.
VSCode has the same command system as atom. These commands can be started through the "command palette" and also bound to a key-combo.
The corresponding command is toggleVim
. You can bind this command to a key using the gear-icon > keyboard combos (sry, i don't know how to switch the language for an exact description :) ) > enter "toggleVim" to the searchbar. Then you can assign a combo to it.
Effectively the extension will be disabled or enabled quickly.