The "it does not work" was not generic it was refering to trying to open a new tab with various combinations of mouse and keyboard buttons, I am sorry if this was not clear from the subject and content of my question. I don't know what else to add as 'it doesn't work' - I followed the instructions in the FAQ and have re-checked them several times but I can't get a new tab to open by double clicking the mouse middle button or any of the other pre-defined commands in the file types menu, such as 'Left double click + alt' do not do anything either.
In addition to 'Go NEWTAB' I think I have tried adding all the commands given in the FAQ to the middle-click option in the file types-all folders-edit-events menu.
Just to be clear, the FAQ I am refering to is: Middle click folder to open in new folder tab