How to change Barrée position in the palettes?

Hello,

while trying some of the features of MuseScore2 beta I was going to put a barrée like VII_____ into a little guitar piece from the lines palette into the score. No problem if you need to mark just the 7th fret. But I haven't found any solution how to change the VII of this palette into something else like II, IV to show other left hand positions.

I've tried to change the palette, to create a new palette, looked into the style menu, looked for some help here in the forum - all without any result. Does anyone know how to resolve this problem?

Thanks in advance
raluc