Locked Tab (allow folder changes) - problem

I must have a NEWTAB argument, or its settings equivalent lurking in my Folder Tabs setup, but I am dashed it I can find it.

I decided to use Locked Tab (allow folder changes), as my standard tab config, but I find that when I click a folder, it always opens a new tab, rather than temporarily using the one I am on. This is the behaviour I have always had with tabs, and I am pretty sure I remember configuring my system to work that way when folder tabs first became available, but now I cannot remember how I did it.

Can anyone suggest how to undo it?

I have kept looking, and have answered my own question.

In File Types/All Folders, I had set the left double click event to: Go NEWTAB=findexisting.

All is well now.