PhD in the Netherlands: Can I negotiate the starting step in my salary scale?
Short answer, no.
Every PhD student starts at the same level, I have never heard of anyone negotiating a higher salary (I did my PhD in the Netherlands). The only two exceptions I am aware of are a) medical doctors doing a PhD - they start at a higher salary - and b) people funded by an outside source like a foreign government or company, where the outside source stipulates and pays the salary.
But a higher salary based on work experience: no. I don't suppose there's any harm in asking if you have already accepted the PhD position, but don't get your hopes up. I actually know one PhD student who has tried it, but she got shut down fast by HR.