In many cases it makes sense to hide rather than remove buttons from a communication board. If the user is new to the board it may make sense to gradually reveal more buttons over time. Hiding and showing has the added benefit of keeping all buttons in the same place (rather than adding a row or column later and causing everything else to shrink to make room) which is very helpful for individuals working on motor planning.
Use the painting tool
The painting tool lets you hide multiple buttons at the same time. While editing the board hit "Paint" to start the tool.
Touch or press down with your mouse and drag around to select all the buttons you would like to hide. They will become semi-transparent when hidden. When you are finished hiding buttons, hit "Save".
You will now see the board as before, but with the selected buttons hidden. The buttons will also be hidden in Speak Mode. Showing is done the same way, only selecting the "Show" instead of "Hide" brush.