You can insert a new item into the current category by clicking Menu: Items⁄New item or by pressing Ctrl Insert on your keyboard.
After performing the insert action, focus will be set to the detail pane (on the right-hand side of the screen). Moreover, the text cursor will be inside the topmost field inside the right-hand pane.
Now you can enter information using your keyboard.
Note: if you insert an item while the 'All data' tab is active, the newly inserted item will not belong to any category. You can always assign another category to an item by Copying and Moving items