How can I set a target order or stop loss relative to the actual trade price of my parent order in TWS?

You can set up percentage based bracket orders within your order Presets. In TWS, click on the Edit menu option followed by Global Configuration. On the left side, expand the Presets section by clicking on the plus sign next to the word presets. Next, click the product type you wish to set up Presets for (e.g. Stocks, Options, etc.). The Presets window will populate on the right side…

You can set up bracket orders with defined offset amounts within your order Presets. In Classic TWS, click on the Edit menu option followed by Global Configuration. On the left side, expand the Presets section by clicking on the plus sign next to the word presets. Next, click the product type you wish to set up Presets for (ex. Stocks, Options, Forex, etc.). The Presets window will populate on the right side. Click the "All possible fields" button at the top of the window to expand all of the sections within Presets. Scroll down to the "Target Order (Profit-taker)" and "Attached Stop Order" sections. Use the various sections (Order Type, Limit Price/Stop Price, Offset Amount, etc). to set up your desired parameters. Once you have set up your bracket order Presets as you wish, click the Apply button followed by OK to close the window…

If you set up your Order Presets with "Apply offset to parent" for your Target Order or Attached Stop Loss, then it is not possible to adjust the order price lines of Take Profit and Stop Loss child orders within TWS charts.

Please note that you can still modify order prices from the Orders window…

Depending on your configured Order Presets you may not be able to modify the price of your open Bracket order's attached legs. In the Target Order (Profit Taker) and Stop Loss Order sections of the Order Presets window there are check boxes for "Apply Offset to Parent". If you check this box the Limit price for Attached Target orders and the Stop price for Attached Stop Loss orders will be set relative to the actual trade price of the Parent order. If your Bracket orders are configured this way you will not be able to edit the prices for the child Stop Loss or Profit Taking legs of your active Bracket order. If you want to be able to modify the prices for the individual attached child legs of a working Bracket order, then you need to leave the boxes unchecked.  …