If you “Display text”, it always draws an image of a piece with the “Does Not Stack” trait, even if “Draw pieces” is unchecked. I found a workaround by reducing the zoom factor to 0, but probably better to fix than for designers to stumble upon that Easter egg. Also “Text below each piece” only works if “Draw pieces” is checked. Again, you cannot display just text.
One more issue is that you cannot remove the border color. If you click cancel to change the color to “nil”, which works in most other editors, once you click OK to save, it “forgets” the change and reverts back to the previous color.
This is bug 13920 and is fixed in VASSAL-3.4.13-SNAPSHOT-b6b5df8fe, available here: