Slide preview is a very useful tool. With that you are able to preview how your slider looks like live. When you press the Enter Preview button, the slider will start from the current slide, and play continuously. This also great to see how the different slides fit for each other in one piece.
There are some controllers in the top bar of the editor area, and the first one is the preview size. You can zoom-in and out of the slider. This can be useful on larger sliders.
When the preview mode is not active this area works as a drag & drop editor area. You can move your layers into the suitable position by your mouse, or even you can also use the alignment feature to place that into the suitable part of the slide. If you use these buttons, the positions will set by percent values under the Styles tab of the layers, which is also useful for the full screen or full width sliders, because with that you can place a layer into the edges of the slider.
Another important buttons the Undo and Redo, which can help you to e.g. get back and item what you have deleted accidentally, or even that yet.
The next buttons are useful if you set up layers, which are not visible on all devices. You can make that easily by click on the device icons on the layer tab. Learn more about that on the following link: Hide layout on specific devices. To preview the slider as mobile, tablet or desktop, just click on the icons, and the active highlighted, while the inactives are grey. You can not only preview the whole slide to able to check the animations, but you can do the same for layers as well, so you don't need to watch the full slide, if you are trying to fine tune the different effects for the current layer.
On the lower part of the editor you can find the Layer manager tool, where you can add different type of layers, and also see the existing ones on the left. Here you can also edit their properties, like style, different Transition settings, or other attributes, like links. You can learn more about them in details under the Layer settings part of the documentation. This part of the editor also can be pop out from this fixed position. This could be useful when you have a larger slider, and would like to also see what you set in the preview at the same time, because in that case the editor can be placed into any suitable position by simple drag & drop.