The Opera developers work in highly unprofessional manner:

Look at Opera 20 so called "help": how to import bookmarks?
or

• type in browser opera:flags , and
  serach "import"
  --
  The developers wrote:

Enable or disable profile import from Opera 12 or other Presto-based Opera versions. Presto's profile location can be given explicitly by passing '--presto-small-prefs-dir=ROAMING_PROFILE_DIR' and '--presto-large-prefs-dir=LOCAL_PROFILE_DIR' to the command line.

This recommndatio of the developmentteam is wrong for Windows 7/8.1.

Still, till 06/03/2014 the developers of Opera were unable to find a solution for the important issue:
how a user may import his/her previuous booknmarks from Opera v.12+ into Opera v.20,
using previous archive or using sinhronization.

Question to developers: when the import of bookmarks tool will be realized?

tag: bookmarks import data migration