Federico hit the point. I forgot to mention in my first message that Frescobaldi is the editor I use and a custom tuning generator would be a very nice addition!
I think that extending the tunings for "unorthodox" tunings is pretty
pointless since that makes finding the needed information harder, and
since it results in basically random selection of predefined tunings.
The point here is more that it is _trivial_ to do your own tuning, by
writing something like
\new TabStaff \with { stringTunings = \stringTuning <c, g, d g b d'> }
{ ... }
It is much faster to write this down rather than searching through
preexisting tuning tables to find a particular unorthodox tuning.
I agree.
But a custom tuning generator in Frescobaldi wizard would be nice: