The plugin is basically meant for Theme designers/developers and not for general purpose with a focus on Bootstrap 3 based themes. It is similar to the Element Library tool.
Acc. to the plugin description –
This tool provides pages containing various elements of Moodle, and the Bootstrap 3 framework, live within Moodle, using your current theme CSS to allow for quickly identifying problems when developing or testing themes.
The plugin can be used for:
- Theme Evaluation
- Theme Development
- Theme testing
- Writing renderers
You can download the Theme tester plugin from this link which is available for Moodle 2.9.
Which tools you are using while developing your Moodle theme? Let us know in the comments below.