All multiple-choice menus in KM have their currently selected item disappearing when I hover the menu in Yosemite (if choices, menu activation, everything really). I can click and then select an action, item or whatever, but until I click the current item remains invisible. Isn’t this a bug?
Yes, this is one of several bugs in Yosemite (see http://www.stairways.com/blog/2014-10-18-yosemite). This one was introduced very late in the development cycle (in DP8, the last one before the GMs). It has been reported to Apple (rdar://problem/18376252), but there is no movement on it at this stage. The only solution I have to it involves the use of private APIs.