These are the actions you can find at the buttons on the top of the layer window or by the layers.
Merge the current layer with the one right below it.
Remove the current selected layer
Add a blank layer or duplicate the current layer.
A shortcut to change to the previous frame without having to open the animation timeline
A shortcut to change to the next frame without having to open the animation timeline
Toggles the visibility of that layer. A hidden layer is also hidden when exporting.