Looking at a new 2019 zforce 800ex. My biggest problem with any sport type UTV is leg room. I'm 6'3" with a 34" inseam. Any taller drivers having leg room issues particularly left knee against the door and right knee against gear shifter? Any mods for leg room issues?

I'm about 4" shorter and with the seat moved all the way back I'm comfortable in it.  Didn't think I would be when I first sat in it but I'm used to it now and don't get sore even after running all day in it.  My left knee naturally rests against the door and it just feels normal.  There is at least 1 guy I know of on most of the CFMoto/Zforce facebook groups (pretty sure he's on here too) who makes seat risers to gain a couple more inches of height, and the ability to move it further back, and from what I hear it's a big improvement for you taller guys. 

[2015 Z Force 800 53/Trail EPS]

I am about 5'7" with a 30" inseam and for me it was a little short but after using some washers and longer bolts to tip the seat-back forward an extra inch or so I was able to elongate the seat adjustment slots another inch or so which was enough for me. I did try some 1" risers on the seat and although it worked, I just didn't like the feel and took them back out. 

I have not seen anyone complain about the gear shifter hitting or rubbing on their right leg. With it shifting forward it seems like it could be an issue.

[2015 Z Force 800 53/Trail EPS]

I have not seen anyone complain about the gear shifter hitting or rubbing on their right leg. With it shifting forward it seems like it could be an issue.

With my slightly straighter leg on the throttle it has not been an issue...and probably never will. If I had to drive "bow-legged" it might be...but then I would have bought a machine that fit better in the first place. My thinking is if you are going to be out 6-10+ hours at a time, then best get something your body can live with. It's worth the extra coin in the long run.

I agree  on the shifter. I am 5'11" and might right knee seems to rest on the shifter too. Not exactly the most comfortable either. The seats to adjust move all the way back. Still not to bad for seating

I'm 6'4" with the same inseam as you and yes, it is tight in there.  My left knee hits agains the door and my right rubs on the dash.  I did, however, fill the foot well to bring it up to the same level as the rest of the floor just to change the angle of my foot when on the gas peddle.  Another couple of inches of room would be nice, so I will try raising and moving the seat back a bit.  I'll also try changing the angle of the seatback to get just a little extra room.  For now, I've adjusted.

I'm going to look at the 800ex again this week. I wont be riding enough to justify spending a lot of money. I don't ride fast or hard, so my only real requirement is a little leg room. Most likely I'll probably do 4-5 trips between Tug Hill NY and upstate NH.

I made it back to the dealer and sat in it again. The only thing I see being an issue is the shift handle. If I could rotate the handle 180 degrees or maybe bend the shifter a little to the right would solve my problem. I would definitely try seat spacers.

There are a lot of aftermarket shifter handles available.  Here's a link to Amazon.  Scroll down to see more than the featured shifter.  Very easy to install. 
https://www.amazon.com/AZQKJ-Universal-Automatic-Operation-Transmission/dp/B01L3DT9TK/ref=sr_1_25?dchild=1&keywords=cfmoto+accessories&qid=1589928316&sr=8-25 

The shifter handle in the link looks perfect. If i get the machine that's the first thing I'm doing along with an air filter upgade.