Where is "Convert to AAC…" in iTunes 11 (and 12)? In iTunes 10, holding the Option key while selecting the Advanced menu turns Create AAC Version into Convert to AAC… which allows selecting a number of files which are then converted to AAC and added to the library. Does this functionality still exist in iTunes 11 (and 12)?
It does, but it's a little hard to find. It's under File -> Create New Version. You still need to hold the Option key. But the difference in iTunes 11 (and 12) is that you have to make sure no songs are selected when you perform the menu selection. If a song is selected iTunes will attempt to create an AAC version of the selected song. If nothing is selected you can select audio files to convert to AAC.