With 2.3-dev (and before that) there are inconsistencies or bugs regarding focus-management.
Open LyX, create new document. Open document-settings. Switch to preamble. There is no focus in the preamble-editing area. It should be active immediately. Activate preamble editing area. Now close the settings window. Reopen document settings window. The editing area now shows a blinking cursor, pretending to be active. But there is no keyboard entry possible. The blinking cursor should always indicate where keyboard action would have consequences. This seems to be a general issue since similar behavior also impedes working with other panels, like find and spell checking. Is this now working as designed, i.e. intended? greetings Mike