View of the element buttons panel depends on wml deck context and currently selected element. Select different elements in the elements tree window and see how buttons changes in the panel.
Each button represents wml element what you can insert in the selected element. In figure you see card button, template button, head and comment buttons available for wml element. Note you can not see others elements in the panel because they are does not allowed in the wml deck.
For instance click on card button. Your new card is created and is ready to be edited. New card appears on code editor window and the elements tree window reflects changes. Click on created element in the the elements tree window and set attributes.
Then click on head button. New head element appears after card element. This looks wrong. You can change placement of the head and card elements using Ctrl+Arrow Up and Ctrl+Arrow Down keys.
See also: Tools panel