Most of it is said before. Don’t be intimidated too much by job descriptions - it is more important to have general awareness and some knowledge and experience, more important usually is that you are a reliable employee willing to enter a long-term relationship. And don’t be intimidated by the amount of knowledge required either, even though there is vast literature on plastic moulding, if you read a few design guides about the materials and processes used by the company, practice with a few parts in CAD you will have a head start. Often these guidelines also depend on the manufacturer and developing the CAD part will happen conjointly with that party since they know all about their machines - for example some factories can produce 0 draft files or certain undercuts because they have more advanced ejection capabilities.