Allowed blocks for core/column

If you’re using WordPress 6.5+, then you can filter the column blocks settings and add allowedBlocks array to it. In the array you’d define all the blocks, which the user can insert into the column.

wp.hooks.addFilter( 'blocks.registerBlockType', 'my-column-blocks', ( settings, name ) => {
  if ( name === 'core/column' ) {
    const { allowedBlocks = [] } = settings;
    return { ...settings, allowedBlocks: [ ...allowedBlocks, 'core/paragraph' ] };
  }
  return settings;
} );