Hi,
In the current version, \placenamedfloat is broken because of a mismatch between lpeg and the user input.
This should work but doesn’t:
\placefigure[somewhere:delta][whatever]{delta}{}
\placenamedfloat[figure][delta]
Whereas this works but shouldn’t:
\placefigure[somewheredelta][whatever]{delta}{}
\placenamedfloat[figure][delta]
Also, this new black-magic-y float stuff is not documented. Since it is experimental I get that, but it seems very handy to me.
Best wishes,
Taco