The F12 shortcut should be included in mainwindow's shortcut table (section 2 of appendix B of manual).
Changes related to this bug have been committed. Please check latest Git and update the bug accordingly. You can also get the patch from: http://git.claws-mail.org/ ++ ChangeLog 2015-02-25 13:51:02.403022723 +0100 http://git.claws-mail.org/?p=claws.git;a=commitdiff;h=21f32abe17b35ab587629410ef48ef0f4479ebb0 Merge: 7c66244 9cbe67d Author: Colin Leroy <colin@colino.net> Date: Wed Feb 25 13:51:01 2015 +0100 Merge branch 'master' of file:///home/git/claws http://git.claws-mail.org/?p=claws.git;a=commitdiff;h=9cbe67d129bd33dc77a80f10fedf6069c5682662 Author: Ricardo Mones <ricardo@mones.org> Date: Wed Feb 25 13:50:16 2015 +0100 Sync Spanish manual translation http://git.claws-mail.org/?p=claws.git;a=commitdiff;h=8cca354e303c3715fb725ddcc0331ede7a733479 Author: Ricardo Mones <ricardo@mones.org> Date: Wed Feb 25 13:49:00 2015 +0100 Fix bug #3389 ‘document 'F12' shortcut’