Is there a way in scribus to center text automatically within a text frame?
I guess you want to center your text vertically.
In the development version 1.5.3, you can set he vertical alignment in the text properties palette, in the "Columns & text distances" sections".
With Scribus 1.4.x (the current stable version) you can use this script:
But, since in most case, you should not overuse centered items, you can also manually tweak the top and bottom distances in the "Columns & text distances" section of the "Properties palette".