Is there a simple way to copy selected paths from all layers and paste into another glyph / font in edit view?
Is the other glyph empty? In that case it might be easier to copy and paste the entire glyph.
No. Not empty. Just glyph parts.
So you would like to merge two glyphs? All the layer contents of one glyph should be placed on top of the layers with the same names on another glyph. There is no built-in feature for that, but a script could do it.
There’s a mekkablue script called copy layer to layer that might help but your mileage may vary.