WordPress Gutenberg - transform core list block to custom block with multiple InnerBlocks.

index.js

transforms: {
        from: [
            {
                type: 'block',
                blocks: ['core/list'],
                transform: ({ values }) => {
                    let entries = values.split('</li><li>');
                    const link_pattern = /<a href=['"]#endnote[0-9]+['"]>([0-9]+)<\/a>/gi;
                    entries.forEach((entry, index) => {
                        entries[index] = entry.replace('<li>', '').replace('</li>', '');
                        entries[index] = entries[index].replaceAll(link_pattern, '');
                    });

                    const innerBlocks = [];
                    innerBlocks.push(
                        createBlock('core/heading', {
                            level: 2,
                            content: _x('Fussnoten', 'Default content', 'sha'),
                        })
                    );

                    entries.forEach(entry => {
                        innerBlocks.push(
                            createBlock('core/paragraph', {
                                content: entry,
                            })
                        );
                    });

                    return createBlock('sht/footnotes', {}, innerBlocks);
                },
            },
        ],
    },