Changing the columns position

To change the position of a single column, tap&hold on that column's header, drag&drop it on the desired position

If you'd like ot move them in bulk, tap on Tools (top bar) > Hammer

Creating new columns at any given position

Tap on the header of the reference column and then on the quick action button below
You will be able to insert columns before or after the selected column

The Column Manager, moving and editing in bulk

You can move multiple columns at once by selecting them first, then Cut, selecting the target position and paste

Frozen columns

A frozen column will always be shown next to the students names.
This will help you keep important columns always on sight while scrolling your grade book.
Tap on Tools > Columns > Drag&drop your columns in the 'Frozen columns' zone next to the 'Student name'.