Yes, slippery elm powder is excellent.
While flaring, I used to use it 3 x per day, after each meal.
Now in remission, I still take it once a day.
You could also add L-Glutamine amino acid powder.
It works great long term for colonic repair, and you can take it on an empty stomach when you suffer from diarrhea.
There are other things you can do as well.
There are things IMO that you can control, which will have a direct impact on your disease, the symptoms you experience and their severity.
I was able to control my UC into remission through various supplements, probiotics, diet modification, and LDN , low dose naltrexone.
For more info on the protocol which has put me into remission, please go to this link: https://www.healingwell.com/community/default.aspx?f=38&m=1666318 , and look at the 11th post.
I hope you feel better and let us know how we can help you.