HSLv1.mq5

// write mql5 code to set SL to entry price of all current position when current price of XAUUSD move more than 20pips.
void OnTick()
{
    double XAUUSD_Price = SymbolInfoDouble(_Symbol, SYMBOL_BID);
    Print("XAUUSD_Price: ", XAUUSD_Price);
    double XAUUSD_Pips = SymbolInfoInteger(_Symbol, SYMBOL_DIGITS);
    Print("XAUUSD_Pips: ", XAUUSD_Pips);
    double XAUUSD_PipsToSL = 20 * Point();
    Print("XAUUSD_PipsToSL: ", XAUUSD_PipsToSL);
    double XAUUSD_SL = 0;
    int TotalPositions = PositionsTotal();
    Print("TotalPositions: ", TotalPositions);
    for (int i = 0; i < TotalPositions; i++)
    {
        ulong Ticket = PositionGetTicket(i);
        if (Ticket > 0)
        {
            ENUM_POSITION_TYPE Type = PositionGetInteger(POSITION_TYPE);
            if (Type == POSITION_TYPE_BUY || Type == POSITION_TYPE_SELL)
            {
                double EntryPrice = PositionGetDouble(POSITION_PRICE_OPEN);
                double StopLoss = EntryPrice - XAUUSD_PipsToSL;
                if (Type == POSITION_TYPE_BUY && XAUUSD_Price - EntryPrice > XAUUSD_PipsToSL / XAUUSD_Pips)
                {
                    StopLoss = EntryPrice;
                }
                else if (Type == POSITION_TYPE_SELL && EntryPrice - XAUUSD_Price > XAUUSD_PipsToSL / XAUUSD_Pips)
                {
                    StopLoss = EntryPrice;
                }
                if (StopLoss != XAUUSD_SL)
                {
                    bool Result = PositionModify(Ticket, StopLoss, PositionGetDouble(POSITION_TP));
                    if (Result)
                    {
                        Print("Position ", Ticket, " SL set to ", StopLoss);
                    }
                    else
                    {
                        Print("Position ", Ticket, " SL not set");
                    }
                }
            }
        }
    }
}

modify.mql5

bool ModifySL(ulong ticket,double new_sl)
{
   MqlTradeRequest request={0};
   MqlTradeResult result={0};
   request.action=TRADE_ACTION_SLTP;
   request.type=ORDER_TYPE_SELL;
   request.position=PositionGetInteger(POSITION_IDENTIFIER);
   request.symbol=_Symbol;
   request.sl=new_sl;
   request.magic=123456;
   request.ticket=ticket;
   bool res=OrderSend(request,result);
   return(res);
}
Here is an example of how to use the OrderSend() function to modify an active trade’s SL in MQL5:

bool ModifySL(ulong ticket,double new_sl)
{
   MqlTradeRequest request={0};
   MqlTradeResult result={0};
   request.action=TRADE_ACTION_SLTP;
   request.type=ORDER_TYPE_SELL;
   request.position=PositionGetInteger(POSITION_IDENTIFIER);
   request.symbol=_Symbol;
   request.sl=new_sl;
   request.magic=123456;
   request.ticket=ticket;
   bool res=OrderSend(request,result);
   return(res);
}

modify2.mq5

// SL & TP Modification
// ref https://www.mql5.com/en/docs/constants/structures/mqltraderequest
// Trade order to modify the StopLoss and/or TakeProfit price levels. It requires to specify the following 4 fields:

// action
// symbol
// sl
// tp
// position
   MqlTradeRequest request;
   MqlTradeResult  result;
   ulong  position_ticket=PositionGetTicket(i);// ticket of the position
   string position_symbol=PositionGetString(POSITION_SYMBOL); // symbol 
//  TODO
//    double sl =
   double tp = PositionGetDouble(POSITION_TP)
   request.action  =TRADE_ACTION_SLTP; // type of trade operation
   request.action=position_symbol;     // symbol 
   request.symbol=position_symbol;     // symbol 
   request.sl      =sl;                // Stop Loss of the position 
   request.tp      =tp;     
   request.position=position_ticket;   // ticket of the position
  //--- zeroing the request and result values
    ZeroMemory(request);
    ZeroMemory(result);
    if(!OrderSend(request,result))
        PrintFormat("OrderSend error %d",GetLastError());  // if unable to send the request, output the error code
    //--- information about the operation   
    PrintFormat("retcode=%u  deal=%I64u  order=%I64u",result.retcode,result.deal,result.order);