The airfields view allows you to enter/edit the airfield dropdown list. Changes made to this list DO NOT change entries where they are used. You must manually change entries where you have used this airfield if you wish to make changes in your logbook.
You can tag as many airfields as you want to transfer to a handheld, but only the first 50 will be synced. A future version of this software will help you automatically select the most used airfields to sync with the handheld.