Since 4.2 version of The Scheduler, you can see the issues that will be created by the plugin by using "Show Upcoming Issues" feature. There are two ways to use it:

Use the drop-down menu cloaked under the "Projects" (1) to access a desired one and then go to the below located "Scheduled Issues" (2).

"Show upcoming issues" (3) is located at the central area of the page.

The following dialog box will appear:

This dialog will list upcoming issues to create in the project. You can choose the amount of issues to list.

Use the drop-down menu cloaked under the "Projects" (1) to access a desired one and then go to the below located "Scheduled Issues" (2). "Show upcoming issues" (4) is visible after clicking "More" (3) link.

The similar dialog as previous will appear:

This dialog will list upcoming issues to be created by the selected Scheduled Issue trigger.