
I made some sample bookmarks [1 to 6] and then used
_pdfViewerKey.currentState?.openBookmarkView();
to view the bookmarks. Here bookmarks which were written in English were shown correctly but the bookmarks which were written in other languages were not shown correctly. These bookmarks are correctly visible in other PDF viewers.
I also tried manually extracting the bookmark titles using
_pdfBookmarkBase.bookmarks[i].title
but then also the titles are exactly as shown in the image and not as expected.