Try allowing blocks to be nested when dragging below, first attempt

docs/designers-developers/developers/data/data-core-block-editor.md

@@ -363,6 +363,18 @@ _Returns_
 
 -   `Array`: ids of top-level and descendant blocks.
 
+<a name="getDraggedBlockClientIds" href="#getDraggedBlockClientIds">#</a> **getDraggedBlockClientIds**
+
+Returns the dragged block client ids.
+
+_Parameters_
+
+-   _state_ `Object`: Global application state.
+
+_Returns_
+
+-   `boolean`: Whether user is dragging blocks.
+
 <a name="getFirstMultiSelectedBlockClientId" href="#getFirstMultiSelectedBlockClientId">#</a> **getFirstMultiSelectedBlockClientId**
 
 Returns the client ID of the first block in the multi-selection set, or null
@@ -1341,6 +1353,10 @@ _Returns_
 
 Returns an action object used in signalling that the user has begun to drag blocks.
 
+_Parameters_
+
+-   _clientIds_ `Array<string>`: An array of client ids being dragged
+
 _Returns_
 
 -   `Object`: Action object.

packages/block-editor/src/components/block-draggable/index.js

@@ -72,7 +72,7 @@ const BlockDraggable = ( {
 			elementId={ elementId || `block-${ clientIds[ 0 ] }` }
 			transferData={ transferData }
 			onDragStart={ ( event ) => {
-				startDraggingBlocks();
+				startDraggingBlocks( clientIds );
 				isDragging.current = true;
 
 				startScrolling( event );

packages/block-editor/src/components/block-navigation/use-block-navigation-drop-zone.js

@@ -13,11 +13,24 @@ import useOnHTMLDrop from '../use-block-drop-zone/use-on-html-drop';
 import useOnFileDrop from '../use-block-drop-zone/use-on-file-drop';
 import useOnBlockDrop from '../use-block-drop-zone/use-on-block-drop';
 
-function getDropTargetBlocksData( ref, getRootClientId, getBlockIndex ) {
+function getDropTargetBlocksData(
+	ref,
+	dragEventType,
+	getRootClientId,
+	getBlockIndex,
+	getDraggedBlockClientIds,
+	canInsertBlocks
+) {
 	if ( ! ref.current ) {
 		return;
 	}
 
+	const isBlockDrag = dragEventType === 'default';
+
+	const draggedBlockClientIds = isBlockDrag
+		? getDraggedBlockClientIds()
+		: undefined;
+
 	const blockElements = Array.from(
 		ref.current.querySelectorAll( '[data-block]' )
 	);
@@ -32,6 +45,12 @@ function getDropTargetBlocksData( ref, getRootClientId, getBlockIndex ) {
 			blockIndex: getBlockIndex( clientId, rootClientId ),
 			element: blockElement,
 			orientation: 'vertical',
+			canInsertDraggedBlocksAsSibling: isBlockDrag
+				? canInsertBlocks( draggedBlockClientIds, rootClientId )
+				: true,
+			canInsertDraggedBlocksAsChild: isBlockDrag
+				? canInsertBlocks( draggedBlockClientIds, clientId )
+				: true,
 		};
 	} );
 }
@@ -41,7 +60,7 @@ function getDropTargetBlocksData( ref, getRootClientId, getBlockIndex ) {
 const ALLOWED_DROP_EDGES = [ 'top', 'bottom' ];
 
 function getBlockNavigationDropTarget( blocksData, position ) {
-	let offset;
+	let candidateEdge;
 	let candidateBlockData;
 	let candidateDistance;
 
@@ -56,29 +75,51 @@ function getBlockNavigationDropTarget( blocksData, position ) {
 		if ( candidateDistance === undefined || distance < candidateDistance ) {
 			candidateDistance = distance;
 			candidateBlockData = blockData;
-			offset = edge === 'bottom' ? 1 : 0;
+			candidateEdge = edge;
 		}
 	} );
 
 	if ( ! candidateBlockData ) {
 		return;
 	}
 
+	const isDraggingBelow = candidateEdge === 'bottom';
+
+	// If the user is dragging towards the bottom of the block interpret that
+	// they're trying to next the dragged block.
+	if ( isDraggingBelow && candidateBlockData.canInsertDraggedBlocksAsChild ) {
+		return {
+			rootClientId: candidateBlockData.clientId,
+			blockIndex: 0,
+		};
+	}
+
+	const offset = isDraggingBelow ? 1 : 0;
+
 	return {
 		rootClientId: candidateBlockData.rootClientId,
 		blockIndex: candidateBlockData.blockIndex + offset,
 	};
 }
 
 export default function useBlockNavigationDropZone( ref ) {
-	const { getBlockRootClientId, getBlockIndex } = useSelect( ( select ) => {
+	const {
+		canInsertBlocks,
+		getBlockRootClientId,
+		getBlockIndex,
+		getDraggedBlockClientIds,
+	} = useSelect( ( select ) => {
 		const {
+			canInsertBlocks: _canInsertBlocks,
 			getBlockRootClientId: _getBlockRootClientId,
 			getBlockIndex: _getBlockIndex,
+			getDraggedBlockClientIds: _getDraggedBlockClientIds,
 		} = select( 'core/block-editor' );
 		return {
+			canInsertBlocks: _canInsertBlocks,
 			getBlockRootClientId: _getBlockRootClientId,
 			getBlockIndex: _getBlockIndex,
+			getDraggedBlockClientIds: _getDraggedBlockClientIds,
 		};
 	}, [] );
 
@@ -92,7 +133,7 @@ export default function useBlockNavigationDropZone( ref ) {
 	const onFilesDrop = useOnFileDrop( targetRootClientId, targetBlockIndex );
 	const onDrop = useOnBlockDrop( targetRootClientId, targetBlockIndex );
 
-	const { position } = useDropZone( {
+	const { position, type: dragEventType } = useDropZone( {
 		element: ref,
 		onFilesDrop,
 		onHTMLDrop,
@@ -108,8 +149,11 @@ export default function useBlockNavigationDropZone( ref ) {
 		if ( hasPosition ) {
 			blocksData.current = getDropTargetBlocksData(
 				ref,
+				dragEventType,
 				getBlockRootClientId,
-				getBlockIndex
+				getBlockIndex,
+				getDraggedBlockClientIds,
+				canInsertBlocks
 			);
 		}
 	}, [ hasPosition ] );

packages/block-editor/src/store/actions.js

@@ -718,11 +718,14 @@ export function stopTyping() {
 /**
  * Returns an action object used in signalling that the user has begun to drag blocks.
  *
+ * @param {string[]} clientIds An array of client ids being dragged
+ *
  * @return {Object} Action object.
  */
-export function startDraggingBlocks() {
+export function startDraggingBlocks( clientIds ) {
 	return {
 		type: 'START_DRAGGING_BLOCKS',
+		clientIds,
 	};
 }
 

packages/block-editor/src/store/reducer.js

@@ -1131,20 +1131,20 @@ export function isTyping( state = false, action ) {
 }
 
 /**
- * Reducer returning dragging state.
+ * Reducer returning dragged block client id.
  *
  * @param {boolean} state  Current state.
  * @param {Object}  action Dispatched action.
  *
  * @return {boolean} Updated state.
  */
-export function isDraggingBlocks( state = false, action ) {
+export function draggedBlocks( state = null, action ) {
 	switch ( action.type ) {
 		case 'START_DRAGGING_BLOCKS':
-			return true;
+			return action.clientIds;
 
 		case 'STOP_DRAGGING_BLOCKS':
-			return false;
+			return null;
 	}
 
 	return state;
@@ -1646,7 +1646,7 @@ export function highlightedBlock( state, action ) {
 export default combineReducers( {
 	blocks,
 	isTyping,
-	isDraggingBlocks,
+	draggedBlocks,
 	isCaretWithinFormattedText,
 	selectionStart,
 	selectionEnd,

packages/block-editor/src/store/selectors.js

@@ -1006,7 +1006,18 @@ export function isTyping( state ) {
  * @return {boolean} Whether user is dragging blocks.
  */
 export function isDraggingBlocks( state ) {
-	return state.isDraggingBlocks;
+	return !! state.draggedBlocks;
+}
+
+/**
+ * Returns the dragged block client ids.
+ *
+ * @param {Object} state Global application state.
+ *
+ * @return {boolean} Whether user is dragging blocks.
+ */
+export function getDraggedBlockClientIds( state ) {
+	return state.draggedBlocks;
 }
 
 /**