Sorry we need a pic and for sure some more info

Is there attic space above your kitchen?? or is the ceiling vaulted?

Yes there is attic space. Not a ton but there is space.

I just added a pic. The vent on the right needs to move about 5' to the left around where the blue tape is.

Instead of moving the existing vent, why not add a new vent?

Because we'd have to make another hole in the roof and that's a whole other project right? ...different inspectors, etc.

That looks more like a plumbing vent than a HVAC vent. It's PVC, not metal. I think you have some issues here. Sure hope that's not filling the house with methane!

It's metal, it's just painted.

You can have the vent make two 90° turns in the attic. So go straight up above the range into the ceiling turn 90° to the right go 5 feet over and go 90° straight up to the existing penetration.

It would be slightly better to not make a pair of 90° angles but shallower angles so that you make a straight line between the penetration into the attic floor and the attic ceiling.

Is it ideal to have two angles in your venting? No. It will cut down on flow. But not enough to cause a serious problem. My 900 CFM vent makes a 90° turn right above the hood and then travels 15 feet across the house and goes outside wall. It works fine.

How big is the vent pipe? It looks like 6". What CFM will your hood be? You will need to make turns if you which will reduce your airflow but depending on the size of the hood, you may be able to live with it. It will also be a little louder.

Good luck!

There seems to be no reason this can't be done in the attic... I am curious as to who is installing the vent??? They should certainly have been able to answer this question for you.....