...found it via the "Insert" menu for the Scripting window (didn't know about that option before). It says:
"COLORBARPOSITION (P: integer). Sets the position of the colorbar: 1=bottom, 2=left, 3=top, 4=right."

This seems to drastically limit the colorbar handling, compared to previous versions, and also the labels cannot be rotated nor disabled. Or is there a new way to specify the colorbar's position and labelling in more detail?

Paricularly for the mosaic view I feel that the simplified control for the colorbar is quite unhandy. As far as I can see one can now only chose to have a colorbar that is, relative to the much smaller mosaic-like arranged brain slices, way to large. In older versions this problem also existed but it was possible to circumvent it by defining the exact size and position of the colorbar in a script via the COLORBARCOORD command, and so one could still obtain a nice figure in an automated and very convenient way. With the new simplified COLORBARPOSITION command, however, this seems no longer possible which (for me) unfortunately renders MRIcroGL's mosaic view useless...

Is there any way to achieve a similar behavior also in the current MRIcroGL version? Or, if not, is there hope that this will come again with a future release? *fingers crossed*