I understand your pain-point, but AFAIK this is just not possible to attain because of the simple fact that the virtualization technologies you mentioned here are of different types.
Hyper-V is a "Type 1" hyper-visor which runs on host machine hardware. Other examples in this category include Citrix XenServer and VmWare ESXi.
Virtual Box is a "Type 2" hosted hyper-visor which runs within an OS. Other examples in this category include VmWare Player.
If you need to toggle b/w these, a restart is eminent.
A quick way to see the mode is by running "bcdedit" from Command Prompt to see the current config.
- To disable Hyper-V run:
bcdedit /set hypervisorlaunchtype off
- To turn Hyper-V back on run:
bcdedit /set hypervisorlaunchtype auto
However, you would need to reboot in both the cases. I just mentioned a easy config way to make you understand what was happening in the boot loader when toggling between the Type 1 and Type 2 hyper-visor modes.