This option allows setting a margin in pips which the market price should get away from the price set by a Pending Orders Fallback operation. Therefore it should be only considered whenever you set the Pending Orders Fallback Pips to a value greater than zero (thus enabling that option).
Recalling a previous scenario: The current market price for EURUSD is 1.3500 and a new buy pending order is set to open 15 pips away from that price, that is, 1.3515. Now consider that you have the Pending Buy/Sell Open Condition input set with a condition like
iMACD(BAR)>VAL(0), meaning, in this particular case, that the bar value of the MACD indicator should be greater than 0. In addition to that, you have the Pending Orders Fallback Pips set to 10. Now consider that the price of 1.3515 is reached (which would mean the expert advisor would try to open the buy pending order) but the MACD indicator conditions are not favorable at that time with the condition set in the Pending Buy Open Condition input. Since you have Pending Orders Fallback Pips set to 10, the pending buy order open price will be moved away 10 pips to the price of 1.3525, so that if the trend remains favorable to our strategy, a new opening attempt for that pending order will be made.
Now consider the following situation:
Imagine that suddenly the market trend reverses and it begins to deviate from the price that was set by Pending Orders Fallback Pips , 1.3525. If you look at this with attention, you will soon realize that the pending order may never get to open if this trend continues in that direction. For this reason there must be a way to make the pending order price to gradually return to its original price (by controlled levels). It is for that same purpose that the Pending Orders Return Margin option exists. By setting it to a certain value in pips you allow that whenever the market price gets that number of pips below the previous pending order open price set (basically like a margin), the current open price will change to exactly that previous price.Taking the example above, consider that we set the Pending Orders Return Margin to 5 pips (reversely away from the previous pending order open price, which was 1.3515). This means that when the price goes down to 1.3510, the current pending order open price (1.3525) will get back to the previous one which was set, 1.3515. This can happen once and again in this leveled manner, just the same way as does the Pending Orders Fallback Pips feature.