Thank you for your review! I am glad that someone think it is convenient.

(1)(2) No. Don't worry about it. This add-on keeps bookmark internally regardless of local bookmark, so it will never mess up your bookmarks. At the same time, however, this add-on can not display local bookmarks...

Coordination with local bookmarks is an interesting feature. I will consider adding it. This feature will search and list up local bookmarks, so you do not have to manage folder for this.

EDIT: This extension now can import/export bookmarks! The feature coordinating with local bookmarks is not yet implemented, but it is possible to import local bookmarks exported from bookmark manager.