New Content Element Wizard
The New Content Element Wizard is TYPO3 Core's standard dialog for choosing and creating a content element. It opens from the create new content element control on a page column or on a Grid Element's own cell, and remains exactly what it has always been: a categorized list of element types an editor picks from.
Grid Elements integrates with this dialog rather than replacing it.
Where Grid Elements appears in it
Opened from a column or cell that allows Grid Elements at all, the wizard's list includes the Grid Element layouts available there, alongside TYPO3's own content element types and any installed plugins. Picking one creates a new Grid Element of that layout, already placed in the column or cell the wizard was opened from.
How structural context narrows the choices
The wizard's list is not the same everywhere. Which content element types, plugins and Grid Element layouts appear depends on the restrictions configured for the column or cell the wizard was opened from. An area limited to a small set of layouts, or one that disallows Grid Elements entirely, simply does not offer the choices it disallows. This is the same restriction configuration described in Restrictions, Validation & Permissions, applied here as it is applied everywhere else an editor creates or places content.
Relationship to the Drag-In Wizard
The New Content Element Wizard and the Drag-In Wizard are two different ways of reaching the same choices, not competing workflows. The New Content Element Wizard remains a valid, ordinary way to create content, opened from wherever it is needed, one element at a time. An editor who uses the Drag-In Wizard consistently while building out a page's structure may simply never need to open this dialog for that part of the work, since the Drag-In Wizard covers element creation directly from the same panel. Both remain available side by side; neither is deprecated in favor of the other.