Trailing shifts the Grid Bots range up for long deal and down for short deals if the price is moving into the grid’s direction and approaching the border levels of the grid. That way the price would stay inside the grid. I.e., the long grid could start with a range 0 - 100 and end with a range 80 - 180.
If the price is moving against the grid’s direction, we cannot have trailing if we don’t want to close the open deals at the opposite border of the grid at a loss. Instead we had to expand the grid by adding additional levels. Above grid could end with a range 50 - 180.