Estimating action duration
If you like, you can note how long you expect actions to take. Then, when you're looking for something to do, you can choose based on how much time you have on hand.
To turn on the time estimate column in the main outline, choose View ▸ Columns ▸ Estimate.
To assign a time estimate, click in the estimate column for an action, then type a duration. By default, the numbers you type are interpreted as minutes (5m and so on). You can also type larger units, like hours (h) and days (d).
To group and sort by time estimates, use the grouping and sorting menus in the view bar.