Seems to work well. Basically just a fancy bookmark that makes it easy to override an existing bookmark with the same name.

In case it's not clear how to use: the addon adds a toolbar button and a sidebar.

Go to any webcomic page and click the toolbar button. Give it a comic name and click "Mark position". This saves the current URL as a bookmark which you can view in the sidebar.

When you navigate to any other page on the same domain, clicking "Mark position" again will update the bookmark with the current URL.