Thank you for reporting this error. As a quicker way of updating a revised element, you can select the original element and assign the new image file to that element. This will maintain all of the actions sets but update the way the element looks.
When you click on the element and see the properties window, below the element's name you'll see an "Image" field that says the name of the image file in your app folder. If you click there you'll be able to select an image from Dropbox, from the app, or from the files on your computer. When the image is changed, the action sets are maintained.
To separate the action sets in the Action Set Manager, indent the selected action set as if you want that group of action sets to be chained after another (click the action set to select it, and then click the arrow that moves it to the right). This will make the action sets listed separately, and you can then control each one.
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