I suggest adding three functions to the turtles: shiftPlace(), shiftPlaceUp(), and shiftPlaceDown(). This would give the turtle the ability to place objects that require the player to press Shift, such as sophisticated backpacks. This could significantly increase the turtle's inventory capacity if needed.

Alternatively, without adding new methods, you could simply add an optional boolean parameter to the existing place() method. When this parameter is true, it would simulate a Shift-click placement of objects:
place([isShift])
Here, isShift is a boolean that, when true, triggers the Shift-click behavior.

I hope this is clear!