Grievance Mess - Next Steps ?

[Seriou]

I put the first grievance of my career in recently- it was fully upheld.
I have put a second grievance in following further shocking (put somewhat predictable) behaviour and am now off with WRS.
I have also landed a new job, and potentially don’t ever have to return to my old job.

Should I resign as normal - if so what happens to my second grievance?
Do I just start my new job without formally resigning ?

Never burn your bridges. Over the whole of your career it could come back to bite you unexpectedly.

Talk to your employer. Explain you have lost faith because of the issues you have experienced and the situation has made you sick. If you are likely to be on sick leave much longer they may well negotiate a much shorter notice period for you. Explain you want to leave on good terms (assuming you due) and negotiate a good reference - you never know when you'll need it.

Terrible advice- people need to
learn they can’t get away bullying and unprofessional behaviour at work . It’s about time people started standing up not only for themselves but co works and service users

How exactly does sabotaging one's own career and earnings stop others from "getting away" with bullying?

Just because you've raised a grievance doesn't mean you can do a moonlit flit to start a new job without even resigning.

I left a job once with no notice instead submitted sick note for stress

I do like the idea of a moonlit flit to be honest !

However, I know I need to maintain professionalism, I just don’t know how to go about it without having my second grievance filed in the HR bin.