CTRL+T - Tab Size
To alter the width of tab settings.
Command
CTRL+T
Action
The Tab Size command changes the number of spaces the cursor is moved each time TAB is pressed while in Input Mode. The default value is three.
When you press CTRL+T, the Status/Command Line prompts:
TAB value (1-10):
Enter a numeric value from 1 to 10 for the number of spaces you want the cursor to move on subsequent Tab Forward commands in Input Mode.