Do you talk to her at all when you are around her? Maybe talking to her in a gentle/soft tone matched with something that gets her to relax (like stroking her?) could get her to relax and be still. Also, with the leg lifted, you could try to encourage her to put it down (not forcefully - maybe just try pushing her gently onto it, forcing her to have to put it down, for balance?) and praise her when she stands on it (even for a short moment) and maybe then over time she'll be still longer, and relaxed longer (is it possible that putting weight on the foot might be making her uncomfortable in any way?).
Another thing that could help is groundwork. I do a lot with my horse now (started about mid summer when my horse went off and was given no turnout and he did not like that so I did groundwork with him to keep him occupied and it really improved his confidence, relaxation as well as responsiveness and rideability, so I continued to do it even after he came back in full work (I followed the method described in one of the courses on https://dressagetraining.tv/ - the equine learning theory course - but there are so many different styles out there - plenty you can look at without paying for. I was doing a different course when that one was added and I like it because it translates into when the horse is ridden)
I found with my horse that just being gentle and patient with him he slowly came to be more relaxed. His deal was more that he went from a very quiet, small, private farm where it was always peaceful, to a showing/boarder/school barn, that was full of people and horses and just everything was totally different. It took a couple months before I can confidently say he was relaxed.
I'm not sure if any of this will help, or if it's anything you are willing to try, but it is what worked for me and my horse. Everyone at my barn is really 'fast paced' and I know a lot of people that don't think much of any of what I've mentioned and plenty of people who think that changing how you talk, changing how you move, or just slowing down a bit won't do anything, but it made all the difference for us, maybe it will for you too. I don't know. Every horse/situation is different, and I don't really know what to tell you without actually being there, but these are just some simple things that come to mind that could help. I'm sorry if I've gone on a bit, I'm not great at explanations.
I have tried leaving her tied for several hours, and hind end yield while tied.
What have you tried so far? (I have an ottb as well, and he wouldn't stand still for me when I got him - I might have some ideas, but just curious as to what you've already tried)
Background information: she has been off the track for almost 7 years, and she doesn't rear or pull back when tied. Just paws, and has an anxious stance of one leg lifted while tensing her shoulder and back.