I feel you pain.
I have recently had issues with Vcarve Desktop setting tabs manually.
I have a two sided design where the flip side is exactly the same tool path as the top side. However, when you set tabs, the tabs need to be exactly placed so that when you flip the stock the tabs exactly align. VCarve makes this harder than it needs to be. Some sort of layout grid for manually placing tabs would be handy.
Another thing that is bothersome with Vcarve Desktop is that it thinks it’s smarter than you are. Consider cutting a letter “O” out of board stock. You can set tabs so that the “O” stays tabbed to the stock because you are likely anchoring the stock in the corners. However, the inner part of the “O” is not likely to be an anchor point. Even if you add tabs to the inside of the “O” to hold the center in place to keep it from being ejected by the bit, the tabs will not be there in the preview nor will they be there in the generated Gcode. I’ve had center parts break free because of this. I would like it to generate tabs where I place them.