What is your workflow/design responsibilities as an IDer?

Yeah, all development companies have a different balance in the value of design vs. engineering.
What I learned is that already at the start of the development trajectory, the design has to be done right.
And that means, influenced by the requirements of multiple stakeholders and departments.

All too often it has gone like
Engineering: this edge cannot be this high because of draft angles
Design: then the electronics won’t fit, so we have to implement a different edge, oh wait, we will get a sink mark, oh wait this factory can add fillers but we have to switch to different suppliers and the design won’t have the same feel to it…

No, the design has to be done right, right from the start.

So, the best thing you can do with a new product development trajectory that has a decent amount of insecurity/risk, is to have design/development sessions with a small team of several people of different disciplines, it is a win-win situation.