Use the source code of B4XDrawer instead of the library (unzip the b4xlib file). See how SideWidth and mSideWidth variables are used. From a quick look it doesn't seem to be complicated to change it at runtime.
I took the original B4XDrawer code from @Erel and modified it to create a new view. This view supports right panel in B4A and B4I. What was often requested. I spend a lot of time in creating views, some views i need by my self, but some views not and to create a high quality view cost a lot of...
www.b4x.com
Update
1.58
Add SetSideWidth - Change the Side width at runtime