TYPO3 Core

I created this https://github.com/derhansen/test_category small extension in order to test/review the patch

I'm a little confused: In your sample extension, you are using a field 'category' in the TCA, but 'category' is missing in columns. Not sure how to test this.

Thema field category is automatically added to TCA by TYPO3\CMS\Core\Utility\ExtensionManagementUtility::makeCategorizable in TCA overrides.

Patch set 1 for branch TYPO3_8-7 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56905

The backport for TYPO3 8.7 is missing the following code in the class \TYPO3\CMS\Backend\Form\Element\SelectTreeElement:

    /**
     * @var array Default wizards
     */
    protected $defaultFieldWizard = [
        'localizationStateSelector' => [
            'renderType' => 'localizationStateSelector',
        ],
    ];

Therefore, the Localization State selector is still not rendered for the category tree in TYPO3 8.7