Is it possible to edit the nodes across multiple characters at once? For example I need to raise the shoulders of /n /m /h a few units, it would be cool to type the string, select the nodes I need and be done with it, instead of repeating the same operation for every glyph 
This is not possible. I see if we can change that in the future.
If I may add a suggestion, this could be a selection mode, toggled by a dedicated tool, similar to the all layers selection tool.
I was thinking in this direction. One problem is how and what to display the info box.
What info box do you mean? The tool description?
The gray info box in the bottom center of the edit view. E.g.: the bounding box of the current selection.
I would expect it to „compress“ all the glyphs in the string to one coordinate system, incl. sidebearings. So if we have /h /n /m with 40|200|30, 40|200|30, 40|250|30, the rightmost node would be on 830 x-axis.
It probably would make sense to limit this function to one line only, or previously selected glyphs in text mode.
I would like to have a globe command to move all glyphs’ position. Just like scale, rotate and shear.
That can be done with the Transform filter.
I think that wouldn’t be too necessary. If it’s just another version of the edit tool (like the Select All Layers) I think one could live without the info box for that particular case. Or if it would break other things if you hide it for the time multiple glyphs are selected, maybe instead you could just have as manny little info boxes as there are glyphs which got a selection?
Generally I think it would be a cool feature, I sometimes wish this as well. Maybe the need for it doesn’t occur toooo often, but once you’re in a situation, it would be awesome to have. 