This tool allows user to create, delete, re enumerate and format captions for images, drawings and tables. It also allows user to create and maintain listings of images and tables in the document.
Detailed instructions on how to use it and how it operates are available here: 

https://zsucic.com/captionmaker

NOTE: The tool uses some "hacks" to make the above features possible, so before using it on a document, please read through the help manual, especially the part about "Captionize" button. 

In any case, if the tool has messed up your document, use the document version history ( feature in google docs ), i.e. 
File -> Version history -> Show version history
to restore an earlier version of the document.