Notice, that the contextmenu of this heading, is different from that of the gallery. That’s because the contextmenu may contain application specific entries.
For example, in case of the gallery, you can customize the number of images in a row. That’s a quick change. Other entries may bring you to a customization page, like the Customize gallery button.
Here, for example, you can change the margin between images, and save it. Watch the gallery. See the difference?
Let’s talk a bit more about this customization page. At the top, you can see the name of the file which you are customizing. Below, you see the type chain. When the left one is active, you are customizing this specific gallery. Going to the other one, you are setting defaults for all galleries on your website.
Let’s go back to customizing our single instance. In each of these blocks, you can customize one setting. The local value is set for this specific gallery, the inherited value comes from higher up in the type chain. Let’s again use the default margin, and save it.
Going back, you will see that the margin block is collapsed and has a gray line on the left. That’s because it is not defined at this level. The aspect ratio is defined at this level, so it is opened, and has a blue line on the left.