It seems to me that the only item that is not actually a button in this window is the list, and I would actually expect that pressing enter on an item in the list would bring up the dialog to edit that item, which it does not.
Pressing ctrl + enter results in the pending changes being saved and the dialog closing, as if pressing the OK button.
This behaviour currently works in the symbol pronunciation dialog which has a similar pattern. However the pronunciation dialog has had to work around an issue in wx that causes this behaviour (according to the comments, wx ticket #3725). This should be trivial to fix, see onListChar in the SpeechSymbolsDialog class.
Due to a bug in wx (see wx ticket #3725) ListCtrl objects swallow
keypresses (including enter). This is resolved by registering an event
handler and forwarding enter presses to the dialog, and allowing thew
ListCtrl to handle all others.
Thanks @ctoth, you raise a good point there. However, for now I think we will try to keep this work flow consistent with the other dialogs. We are planning on re-working the UI shortly, and we will take this into account during that process.
As a side note, you can press alt+e to edit an item directly.