You can modify the details of the Stop Loss Trigger Price but not the Leg1 Market order that you had placed initially as the market order would get traded the moment it is placed. If you have placed Leg1 super multiple order as limit then even first leg order will be available for modification in case if its partly/not traded. Even in the Stop Loss trigger price modification is possible and but not the quantity.
For Example- Case 1: If you have placed a Super Multiple order to buy 100 Qty of ABC at Rs.1500 and defined Stop Loss trigger price as Rs.1480. You can modify this Stop Loss trigger price to Rs.1479.
Case 2: If you have placed Super Multiple order to buy 100 Qty of ABC at Limit price of Rs.1500, defined Stop Loss trigger price as Rs.1480 & if the trade has been executed partially then you can modify the Stop Loss trigger price by keeping minimum 1% gap of the Limit buy order and you can also modify the Buy order by keeping minimum 1% gap from stop loss trigger price.