First of all - hello python-ideas. I liked the look of the archives, so I thought I'd chip in, if it's OK.
And what about:
<f locals>.g and <<xyzzy locals>.f locals>.g
In the end I like the non-nested version better.
xyzzy.<local f>.<local g> or, preferably, xyzzy.<instance.f>.<instance.g> It's non-nested, shows the locality and maps the locality to the variable.
If not showing function instances is disliked, maybe drop the period between the function and "<locals>" from yours: xyzzy<locals>.f<locals>.g or, again, xyzzy<instance>.f<instance>.g
I think this is just cleaner than: xyzzy.<locals>.f.<locals>.g because it doesn't imply that xyzzy has a single set of locals - especially using <instance>.