core-bundle/src/Resources/contao/classes/Backend.php
public function addCustomLayoutSectionReferences()
	{
		$objLayout = $this->Database->getInstance()->query("SELECT sections FROM tl_layout WHERE sections!=''");

		while ($objLayout->next())
		{
			$arrCustom = StringUtil::deserialize($objLayout->sections);

			// Add the custom layout sections
			if (!empty($arrCustom) && \is_array($arrCustom))
			{
				foreach ($arrCustom as $v)
				{
					if (!empty($v['id']))
					{
						$GLOBALS['TL_LANG']['COLS'][$v['id']] = $v['title'];
					}
				}
			}
		}
	}
public function addCustomLayoutSectionReferences()
	{
		$objLayout = $this->Database->getInstance()->query("SELECT sections FROM tl_layout WHERE sections!=''");

		while ($objLayout->next())
		{
			$arrCustom = StringUtil::deserialize($objLayout->sections);

			// Add the custom layout sections
			if (!empty($arrCustom) && \is_array($arrCustom))
			{
				foreach ($arrCustom as $v)
				{
					if (!empty($v['id']))
					{
						$GLOBALS['TL_LANG']['COLS'][$v['id']] = $v['title'];
					}
				}
			}
		}
	}
Add the custom layout section references