It is possible to set up strategies using Deltas, dollar amounts, or percentages prices of the underlying. See below:
You can also combine the way you specify each leg. To set up legs independently, click on the contract tab to configure that leg. See below:
You can also set up one leg in Deltas. Then use that first leg as a reference to place a second one at a fixed dollar difference. To achieve this result, you must link the second leg to the first one.
This is particularly useful if you want to backtest a fixed width vertical spread, for example. You can set up the first leg as a short Put @ 30 Delta and then set the long leg at a 5 dollars difference from the short leg. See below:
Use this same technique to set up calendars. See below: