These bars or part of certain title styles. In Movie Edit Pro 15, switch to the "Title" tab of the mediapool (in the upper right-hand part of the screen) and you will find a bunch of title styles e.g. in the "Captions" sub section that feature different shapes and colors of these text backgrounds.
How many do you have in the mediapool under said "Captions" section? Are you using the "Plus" or classic version of Movie Edit Pro 15? Download or disc version? I'm using a Movie Edit Pro 15 Plus disc version here, and I'm counting 12 items just under that "Captions" section. Does it cover the one you saw in the demo video?
What do you mean when you say that cannot be edited? Each of these templates is a preset made up of a text object and some other items (e.g. video clip for the colored band animation). If you look at the timeline view, you will see all the tracks. You can reopen the title editor by using the title editor button or double-clicking on the title object.
But what do you mean when you say they cannot be edited? You cannot edit the text and it will always just display the default dummy text?
Make sure you're looking at this in timeline view. When you insert one of these text fx with the colored background bar, it will put a combined object into your arrangement that easily takes up three tracks. You can highlight this grouped object and press the "T" icon in the bar (title editor) or you can double-click on the lowest track of the combined object, which is the actual text track and will also bring up the title editor.
By design, I'm afraid there isn't that much that can be done to those bars in the way of editing. They're not scripts that are supposed to be customized and rendered in real-time. They're pre-rendered motion video clips. So, the possibilities to change their appearance are somewhat limited. You can only ungroup the whole cluster of objects that gets created in the timeline (shortcut: CTRL+M) when you import one of those caption title presets and then select the object with that background video clip (usually the second one of the objects associated with the title) to apply individual effects to it, just from the regular video effects that you could apply to any object (e.g. manipulating the color or contrast).