It's a config pack choising dialog. Every config pack is a set of images/musics/sounds/scripts/parameters. Just choice "SMBX 1.3" to use standard graphics set from SMBX 1.3.
If you need access to stuff from SMBX-38A (Remember, 1.4.x is SMBX-38A), you need to install this config pack
and then choice it. If you will don't choice "Ask every startup", next start editor will use previously selected config pack automatically. But you can toggle it from Configuration -> "Change configuration..." menu.