To change the position of a single column, tap&hold on that column's header, then select the Tools/Spanner option.
You can also open this column manager with a tap on Tools/Spanner (top bar) > Columns
Creating new columns at any given position
The Column Manager
You can move multiple columns at once by selecting them first, then Cut, selecting the target position and paste
Frozen columnsA 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'.