Hi,
Glad you find the 1.3.4...
As AMR is still banned from google, the 1.2.99 version which allows you to move your manga list to 1.3.XX does not exists...
So, the only way to keep your manga list is to use synchronization.
Disable AMR V1.3.XX and go to AMR V1.2.XX options. Click on enable synchronization in the "Synchronization" panel.
Wait for a bookmark to appear (in the bookmarks manager, you will see a bookmark named "All Mangas Reader.XXXXX" in "Other Bookmarks > BSync" folder.
Once this bookmark has been created by AMR, disable AMR V1.2.XX and enable AMR V1.3.XX.
Enable synchronization in AMR V1.3.XX, your manga list will be automatically filled with your old data. (You can disable synchronization then...)
Tell me if you encounter any issue...
Enjoy !
Edit : sorry, I didn't read your full post... hope it will help someone else

))