The creation list for GCM deco is missing due to the recent patch, but there is a workaround. Click on the lvl 1 deco and find the little round bubble on the top right of the item icon. Left click it and you will see 2 options - Resource + Create. Click on Create, and it will bring up a menu where you can create a lvl 2 deco like before.
Thank you for reporting this to us! We are already aware of the issue and have since reported it to our developers for a fix.