The Estimated field in Microsoft Project lets you identify tasks for which dates aren’t yet set in stone:
Simply place a “Yes” next to tasks that are estimated, and leave everything else alone. If you want to make a distinction between estimated and firm tasks in your OnePager chart, you can do so with conditional formatting.
To launch conditional formatting, go to Home > Chart Properties > Task Bars, and then click the Manage Rules button in the bottom. We’re starting out with some conditional formatting rules that assign different colors based on the Status field:
Click OK to close the Conditional Formatting Rules screen, and then click OK again to close Chart Properties. Your chart will update so that all estimated tasks appear with a dotted black border, while still retaining their main colors that are based on status: