If you use the +/- keyboard short cut, the "current" parameter is incremented or decremented in the Panel.
e.g. You can quickly change the exposure using keyboard short cuts. You can change any single parameter in the Panel and you can navigate between parameters using , (comma) . (full-stop / period).
The parameter title in the Basic Panel becomes bold after the parameter adjusted with the sliders. This seems to mark "focus" for keyboard +/- changes.
However if you move to the next image (with left / right arrow keys), the highlighted parameter is cleared so it isn't immediately obvious which parameter now has focus. If you press +/- it will adjust whatever was previously the focus.
You can manually click the title of the parameter and it will become bold and that parameter can now receive increment / decrement events. However, there is a delay of about 0.5s before that becomes bold (unclear if that is actually a transition or just a delay).
So the issues are:
Parameter which will receive the +/- modifier key events loses visual bold focus, so there are times when you are guessing which parameter is about to be changed (go to next image) - so focus should always be visible unless the +/- events are intended to be ignored
There's really no need for such a long time delay to enabled focus when clicked - it should be instanteous since it is responding to a click
There's a confouding situation when the mouse hovers over the parameter slider it makes the title bold, but a different (previous) parameter receives the increment/decrement keyboard events - the interface is inconsistent because the bold no longer flags which parameter is receiving the keybaord change. Hover to re-route events would make the interface really efficient
A good thing is that if you have one parameter receiving keyboard events you can still use the sliders to adjust a different parameter and keyboard focus is fixed to the other parameter.
With #3 there could be some "smarts" which intelligently allow a hover-over parameter change that is "spring loaded", once done keyboard events revert to the previous setting. Hover and using the sliders are two different interactions.