I have this problem from time to time and wonder what I must be doing wrong. I select a paintbursh, but then cannot find the area in the dockable (or docked) window to adjust the size, etc. There is a scroll button, but it only scrolls that part of the dialog that shows the available brush shapes. How do I access the rest of the dialog so that I can adjust the brush size. The opacity “slider” is showing, but not much else.
I think there is a button somewhere to make the whole dialog appear, but I cannot remember where it is.
I have been using 2.9x for some time. An update to Ubuntu 17.10 yesterday replaced that version with 2.10 RC#1 which is fine by me. Now, I just need to get past this one little issue which I think is not really related to the version of Gimp that I’m using. It’s something I’m doing wrong.