Themes come with preset settings of the background, position of your captions, their colour, filters, provided by Rocketium. You don't need to work around on your animations, frames or the things mentioned above.
All of these themes, since rolled out by Rocketium, are saved under the Themes section.
Apart from this, if you have applied a theme and want to change a certain animation/filter in a certain scene, you will not be obligated from doing that.
Once you make changes to this theme, by applying various changes in scene animations/filters/background colour, it won't be the same theme anymore.
Since this becomes a different theme now, you can save this theme to be used again, saving you the same effort in future.
Save it as:
You can find this saved theme under the 'Themes' section next time you make a video.