currently I have the code:

@RangeConstraint(min = 0.1, max = 100.0)
public double multiplier= 1.0;

This renders as a slider but the "step" value is 0.01 (2 decimal places) and I want to know if there's a way to set it to 0.1 (1 decimal place).

This is now available as a new property on the annotation in 0.10.0 and onwards
Cheers