Explanation: 
Prevents users from accidentally deleting folders selected in the navigator.

There is no UI equivalent for DisableDelKeyForNavigator. 

Default: 
If DisableDelKeyForNavigator is absent or set to 0, folders selected in the navigation pane can be deleted.

Recommendation: 
Add DisableDelKeyForNavigator=1 to NOTES.INI. The simplest way to accomplish this is via a Desktop Settings document in an (Organizational) Policy document.

Restrictions: 
This configuration is valid for Notes and Domino 9.0 Social Edition and beyond.