…gone it all through in Engraving options/chords.
Where is the option to control the gap between the letter and the 7
It’s so simple, i’m afraid… but blind 
Oups, so it’s rather complex…
No solution offered in this thread, any ideas?
Shift+X again…?
No, your solution would be to edit that particular chord in the chord symbol editor that Daniel mentioned.
Engraving options, chord symbols, scroll all the way to the bottom. It’s a little bit cumbersome, but definitely gives you full control over that chord every time it is displayed in your project.
If it doesn’t appear but once or twice, you could switch to engrave mode, double click on the chord symbol, and edit it manually.
Ahh, yes, we have this well hidden chord editor, thanks.
Well, it is intended to be a last resort!