The area that your finger needs to touch in in the right sidebar drag handle is very little which makes me have to try 3-4 times before finally grabbing on to the sidebar so I can move it away or into the screen.
Can you make the sidebars drag outer bigger so it’s easier to grab? Perhaps for both the left and right side.
Is the gray grip half way down not big enough? You can either click it or drag it.
This annoyed me, too, the gray handle is a very small target that is hard to hit.
Fortunately, you don’t have to 
Just tap anywhere in the writing area (without interacting with the gray handle first!) and drag that to the left or right. It will eventually drag the right or left sidebar into view with it.
You can use the same technique to make either sidebar vanish.
That turns your entire screen into your target and if you cannot find this ……you have a much bigger problem 
Hope this helps