Just to add on to Nordlys Jeger awnser
I've created a little script so that when you press the Capslock key it will send Win + Space
You will need to install AHK its great for remapping keys.
Once AHK is installed open notepad and enter the code below and save it as a .ahk file and run it.
CapsLock::
Send #{Space}
Return
CapsLock:: will excute the code below when Capslock is pressed
Send #{Space} will press Win + Space
Now you just have to press Caplocks to change between the keyboards of your choosing.
If you would like to know more about what keys you can use you can read more about it Here so you can change it to an F-key if you like :)