When I click to add an adjustment, no dialog appears and the adjustment is not added to history. The pictures showing a few possible adjustments appears in the list, but I rarely use those. Two screen shots are attached. The older show the right hand side of the screen after a crop operation that seems to work fine. Then I clicked on the "Levels" adjustment. The second screen shot shows that the click had the effect of offering a few possible adjustments. As you can see in the history below, the program did not add the levels adjustment when I clicked, and the dialog box used to make the adjustment does not appear.
I am using version 1.9.0 of the software according to the "About" information. Is that the latest?