[roger64]

Here two joint screenshots to help (FontForge)
Pasting the 32 space in the 8239 box (with red cross) was just enough. No need to drag any line*. Paste, the cross disappears, the box is yellow, then generate the same font.

EDIT 23/05 Dragging the vertical line, for example from 250 to 125 (Regular), reduces the nnbsp width and is indeed useful. Sorry for this mistake. Other information is still OK.