first, grab an item with [insert pick up item key]
then find your 2nd item and look at it until [GRAB (key)] pops up
then pause, and press [pick up item] key

this can be done with as many items you want and all of the item in the game

this can make some glitches like PICKAXE and BAT is infinite flight

or by reloading the game with the metal propeller, therefore repleneshing the other 3 in the map, making 4 propellers, you can stack them for super jumps and PEAK movements

Pair that with a pickaxe and you can rocket and use the pickaze to cling onto the sky

its overall pretty fun