or press CTRL+SHIFT+D (CMD+SHIFT+D on Mac)
If you have the XController there is also a dip switch where you can disable “reduced idle current”, this one should be switched to OFF so the steppers get full current when idle. That and making sure $1=255 as Neil stated should do the trick.
The value for $1 is how long a motor stay energized after a move, before it is turned off / get no current. The value represent time in milliseconds, so $1=10 or $1=50 mean 10 / 50ms. The value 255 = ON all the time which is what you want.