How to change the name of the active scheme in Xcode?

XCODE 9:

Product -> Scheme -> Edit Scheme

Or simply click and hold left mouse button on your project icon (on the right from the run button) and select Edit scheme

This is in the Xcode documentation available from the "Help" menu. Choose "Help" > "Xcode Help", then enter "rename scheme" to find it. Here are the steps:

1. Choose "Edit Scheme" from the "Product" menu.
2. Click on the "Manage Schemes…" button
3. Select the scheme whose name you wish to change
4. Press the "Return" key

It will select the name of the scheme and allow you to edit it.