pyqgis-copy-item-to-xml.py

# Run from project origin
layout_name = "your_layout_name"
project = QgsProject.instance()
manager = project.layoutManager()
layout = manager.layoutByName(layout_name)

def duplicate_item(item, layout, position=None):
    doc = QDomDocument('Clipboard')
    element = doc.createElement('Copied items')
    context = QgsReadWriteContext()
    item.writeXml(element, doc, context)
    if type(item) == QgsLayoutItemGroup:
        for subitem in item.items():
            subitem.writeXml(element, doc, context)
    if type(item) == QgsLayoutFrame:
        selected.multiFrame().writeXml(element, doc, context)
    doc.appendChild(element)
    layout_items = doc.elementsByTagName('LayoutItem')
    for i in range(layout_items.count()):
        item_node = layout_items.at(i)
        if item_node.isElement():
            item_node.toElement().removeAttribute('uuid')
            item_node.toElement().removeAttribute('groupUuid')
    layout_frames = doc.elementsByTagName('LayoutMultiFrame')
    for i in range(layout_frames.count()):
        item_node = layout_frames.at(i)
        if item_node.isElement():
            item_node.toElement().removeAttribute('uuid')
            item_node.toElement().removeAttribute('groupUuid')
    layout_childframes = doc.elementsByTagName('childFrame')
    for i in range(layout_childframes.count()):
        item_node = layout_childframes.at(i)
        if item_node.isElement():
            item_node.toElement().removeAttribute('uuid')
            item_node.toElement().removeAttribute('groupUuid')
    return doc

item = layout.selectedItems()[0]
# Alternatively if set item id
#item = layout.itemById('item_id')
with open('/tmp/shared_item.xml', 'w') as outfile:
    outfile.write(duplicate_item(item, layout).toString())

# Run from destination project
# Paste section from file
layout_name = "your_layout_name"
project = QgsProject.instance()
manager = project.layoutManager()
layout = manager.layoutByName(layout_name)

def copyFromXml(file_path, layout):
    doc1 = QDomDocument();
    file = QFile(file_path)
    doc1.setContent(file)
    file.close()
    layout.addItemsFromXml(doc1.firstChildElement(), doc1, QgsReadWriteContext())

copyFromXml("/tmp/shared_item.xml", layout)