I'm having trouble with chossing the number of columns when inserting text in the Gridder. In older Lay Theme versions, it was possible to choose the number of columns with the mouse (and to modify them later on). I cannot change the size when I try using the "-" or "+" keys as instructed, and moreover it is impossible to modify the number of columns once text or images have been inserted.
I use Firefox 49.0.1 on a MacBook Air, OSX Yosemite 10.10.5
Thank you for your help!
All the best,