In the Designer help files it says
To create a pixel selection from a drawn line or shape (path).
1. Do one of the following.
• Using the Pen tool draw a curve or closed shape on your page.
• Select a previously drawn curve or shape and then select the Pen Tool.
2. From the context toolbar, tap To Selection.
OK, where is it?
I know the Designer grey on black interface is notoriously hard to see, but this is ridiculous