Question: Can I limit/manage slippage on MT4/MT5 by setting up "deviation" numbers?
No, but the “Deviation” parameter on MT5 will control the maximum price difference of the price of a prepared order and the market one.
If the price is different beyond the parameter you have set, then the position will not be opened.
You can even set the parameter to zero, so you can make sure that your orders are always executed at the price you have ordered.
Slippage happens when there is no enough liquidity in the market for your order to be executed.
Even you have made an order exactly at the market price, slippage can change the executed price.
