If you are in build 0158 then all you have to do is go to the keypad layout and tap on the cartridge and from the cartridge dropdown list select used cartridges to see all the cartridges in the design.
But if you are in any build after 0142 (including 0158) then the way to see is by selecting the image on the mat and going back to the keypad layout. There you will find the image on the queue. Hold the image with your stylus and you will see a square with the cartridge name in it pop up most probably coming up right under your hand lol . But for some like for me in 0155 , this didn't still do it. So if I pressed on the zoom button when I held the image over the stylus then I could see the cartridge name pop up right enough. You can let go of the stylus and then tap on the cartridge name pop up box and it will take you to the cartridge .
But as of yet you cannot get the exact key - button but it does bring up the keypad layout of the particular creative feature and so is still an improvement from what we first had.
Hopefully this feature, hide & contour and selectively switching off of the template feature in each page will come soon (the last one particularly bugs me the greatest :) ).