An excellent extension that is close to the original Reading List Firefox that Mozilla discarded for Pocket.
Can it synchronize using Firefox Sync? In options this option does not appear and I know that it can be because with the "New Tab Tools" extension in Options it adverts me that this extension is modifying the New Tab page.
I would really appreciate it if you could and you could answer this question.
Thank you.

Edit 1 (29/05/2018): I have been able to verify that the synchronization works halfway. I sync the bookmark in "Bookmarks" but the item is not shown in the sidebar of the reading list.