IntelliJ on Windows doesn't have task dependency diagram gradle button?

Please refer to https://www.jetbrains.com/help/idea/work-with-gradle-dependency-diagram.html. Make sure the required plug-ins are enabled.

The button becomes available when you select a project in the tree:

Note that this feature is not available in the Community Edition. See https://www.jetbrains.com/idea/features/editions_comparison_matrix.html.