Why is the rectangle tool missing from DxO OpticsPro 11 ?

The rectangle tool is one of the features included with ViewPoint, which is no longer included as part of DxO OpticsPro.

To get perspective correction tools, we recommend that you download ViewPoint 2, which is available as a powerful standalone program and as a plugin to DxO OpticsPro 11.

If you're currently using DxO OpticsPro 9, you can also upgrade to version 11, which includes ViewPoint 1 free as a plugin.