well... I don't really think those buttons are needed... you didn't change other stuff besides that.. "non-existing" menu items could include a dummy text.. such as "double-click to add new" or something... Or a context menu on right click...
Quick-N-Dirty compromise might just be to change the group box text from "Add Menu Item" to Add Menu Item (Double Click to Add or Edit).
Honestly as far as ListView controls go double clicking to trigger the default action has always been a rather common behavior in any application I've ever encountered. *Shrug* So after having been there for 10 years it now has 1 complaint ...... It's up to you man.
Double click to use the default
action. That means there's always another, more easily discovered way to do it. And Add/Edit/Delete buttons extremely standard, to the point that I haven't encounter an editable list that doesn't have them (even if they are in the form of icons like an X and a + sign). I cannot think of any example.
Plus, there's just the fact that there's a ton of whitespace over there, taking up space for no reason. Why not make that whitespace functional? I didn't have to move a thing to fit those buttons in. If you didn't have room for the buttons, I could understand making a different choice.
And I would guess that you haven't had any complaints because most people don't use the feature. People who want T-clock generally aren't looking for a program launcher. They are looking for a replacement clock. Program launching is a nice feature if you find it, but not in any way essential.
All of that said, a compromise of indicating the double click feature in any way would be nice, if not ideal. It would at least make it discoverable. The way I'd do it is to both add "(double-click to edit)" to the top, and put a dummy "Add new item" entry at the bottom of the list. But it would still be good to be able to delete directly from the list, and not have to open the edit dialog, and I'm not sure what you would do about all that extra whitespace.
And, no matter what you do, I think the Menu Item Details tab is not so great. It doesn't work like a tab--you can't use it separately from the Quicky Menus tab. It's what made me think the program launcher feature was completely broken. Remember, this is a hack of a hack--the idea that some things may be broken is built in.
BTW, if you really want to get user friendly, you need an installer. There are so many people I would recommend this software to, except they would not know how to install it. The portable version is nice, but a fully installed version would be nice, too.
Heck, if you want, I might work on it--assuming my illness doesn't get in the way of doing work again.