Percentage increase or decrease in tempo

I think one needs to use the function “Process Tempo” for this.
It can be found in the Tempo Editor.

Select all tempo events first, open the dialog, change the parameter “New Length” in such way that the underneath “Equivalent Tempo Scaling” reads either 0.94 (6% slower) or 1.06 (6% faster).
Click “Process” when all is set.