When trying to activate colour enhancement, Make Squiggly gives an error.

dinasset
No error message for this box but with the "toggle" box, Gimp closes!

Also:
parameter GradienNormSmoothness, user enters 0.1 but 1.0 is applied (same for 0.5>5; no float value when apply)

Thanks for reporting, it should be fixed now (after a filter update).
About entering floating point values : depending on your current locale, it may happen you need to write '0,5' rather than '0.5'
(it happens for me, with a French locale). This is dependent on how Qt manages the locale for the widgets.

Thanks David.
Everything OK.