PR# 10953 Backspace key is non-standard in Preferences

In the Preferences window, hitting the backspace key behaves differently from the Cluster tool and the Project Settings tree.

Normally, if a sub-node is currently selected, hitting the backspace key causes the parent node to be selected. This is great, because it's an extremely quick way to move up to the parent level if the selected sub-node is towards the end of a long list of children.

In the Preferences window, hitting the backspace key in this situation has no effect. This is a nuisance, because I have to hold down the up arrow key for some time, then release it at precisely the correct moment, in order to select the parent node.