How to use the @ckeditor/ckeditor5-utils/src/dom/insertat function in @ckeditor/ckeditor5-utils

// Inline filler element has to be created as it is present in the DOM, but not in the view. It is required
		// during diffing so text nodes could be compared correctly and also during rendering to maintain
		// proper order and indexes while updating the DOM.
		if ( inlineFillerPosition && inlineFillerPosition.parent === viewElement ) {
			addInlineFiller( domElement.ownerDocument, expectedDomChildren, inlineFillerPosition.offset );
		}

		const diff = this._diffNodeLists( actualDomChildren, expectedDomChildren );

		let i = 0;
		const nodesToUnbind = new Set();

		for ( const action of diff ) {
			if ( action === 'insert' ) {
				insertAt( domElement, i, expectedDomChildren[ i ] );
				i++;
			} else if ( action === 'delete' ) {
				nodesToUnbind.add( actualDomChildren[ i ] );
				remove( actualDomChildren[ i ] );
			} else { // 'equal'
				// Force updating text nodes inside elements which did not change and do not need to be re-rendered (#1125).
				this._markDescendantTextToSync( this.domConverter.domToView( expectedDomChildren[ i ] ) );
				i++;
			}
		}

		// Unbind removed nodes. When node does not have a parent it means that it was removed from DOM tree during
		// comparision with the expected DOM. We don't need to check child nodes, because if child node was reinserted,
		// it was moved to DOM tree out of the removed node.
		for ( const node of nodesToUnbind ) {
			if ( !node.parentNode ) {

// Inline filler element has to be created as it is present in the DOM, but not in the view. It is required
		// during diffing so text nodes could be compared correctly and also during rendering to maintain
		// proper order and indexes while updating the DOM.
		if ( inlineFillerPosition && inlineFillerPosition.parent === viewElement ) {
			addInlineFiller( domElement.ownerDocument, expectedDomChildren, inlineFillerPosition.offset );
		}

		const diff = this._diffNodeLists( actualDomChildren, expectedDomChildren );

		let i = 0;
		const nodesToUnbind = new Set();

		for ( const action of diff ) {
			if ( action === 'insert' ) {
				insertAt( domElement, i, expectedDomChildren[ i ] );
				i++;
			} else if ( action === 'delete' ) {
				nodesToUnbind.add( actualDomChildren[ i ] );
				remove( actualDomChildren[ i ] );
			} else { // 'equal'
				// Force updating text nodes inside elements which did not change and do not need to be re-rendered (#1125).
				this._markDescendantTextToSync( this.domConverter.domToView( expectedDomChildren[ i ] ) );
				i++;
			}
		}

		// Unbind removed nodes. When node does not have a parent it means that it was removed from DOM tree during
		// comparision with the expected DOM. We don't need to check child nodes, because if child node was reinserted,
		// it was moved to DOM tree out of the removed node.
		for ( const node of nodesToUnbind ) {
			if ( !node.parentNode ) {

function addInlineFiller( domDocument, domParentOrArray, offset ) {
	const childNodes = domParentOrArray instanceof Array ? domParentOrArray : domParentOrArray.childNodes;
	const nodeAfterFiller = childNodes[ offset ];

	if ( isText( nodeAfterFiller ) ) {
		nodeAfterFiller.data = INLINE_FILLER + nodeAfterFiller.data;

		return nodeAfterFiller;
	} else {
		const fillerNode = domDocument.createTextNode( INLINE_FILLER );

		if ( Array.isArray( domParentOrArray ) ) {
			childNodes.splice( offset, 0, fillerNode );
		} else {
			insertAt( domParentOrArray, offset, fillerNode );
		}

		return fillerNode;
	}
}

function addInlineFiller( domDocument, domParentOrArray, offset ) {
	const childNodes = domParentOrArray instanceof Array ? domParentOrArray : domParentOrArray.childNodes;
	const nodeAfterFiller = childNodes[ offset ];

	if ( isText( nodeAfterFiller ) ) {
		nodeAfterFiller.data = INLINE_FILLER + nodeAfterFiller.data;

		return nodeAfterFiller;
	} else {
		const fillerNode = domDocument.createTextNode( INLINE_FILLER );

		if ( Array.isArray( domParentOrArray ) ) {
			childNodes.splice( offset, 0, fillerNode );
		} else {
			insertAt( domParentOrArray, offset, fillerNode );
		}

		return fillerNode;
	}
}