[theducks]

Any line that starts with a hashmark (#) is a comment and is ignored

eg;
#The choices you can have are:
#doubleclick_on_library_view = 'do_nothing'
doubleclick_on_library_view = 'edit_metadata'
#doubleclick_on_library_view = 'edit_cell'
#doubleclick_on_library_view = 'open_viewer'

the only line above that is not 'commented-out', is the one with?:

Spoiler:

'edit_metadata'

BTW the part that you need to change in a tweak is always after the '=' sign