2) In Preferences ==> Advanced ==> Tweaks:
Code:
#: Completion mode when editing authors/tags/series/etc.
# ID: completion_mode
# By default, when completing items, calibre will show you all the candidates
# that start with the text you have already typed. You can instead have it show
# all candidates that contain the text you have already typed. To do this, set
# completion_mode to 'contains'. For example, if you type asi it will match both
# Asimov and Quasimodo, whereas the default behavior would match only Asimov.
completion_mode = 'prefix'