Selecting multiple layers in the GRASS GIS wypython layer manager has always been possible. But there wasn’t much point to it. You couldn’t do anything with the multiple selections, no zooming, removing nor setting the region for multiple layers. Trying to remove all selected layers for example would just remove the first of the list of selected layers.
This missing feature has always bugged me. But stupid enough, I have never taken the trouble to file a bug or feature request. Luckily somebody else did make the effort to file a feature request. And guess what, 36 hours after the ticked was opened, it has already been implemented! Pretty amazing I think.
I tried out r53064 for grass7, but from what I understand, this will be back ported soon (or perhaps it has already been back ported by now).