Enable confirmation box when remove block

Nope, but you can extend the default tlb-delete command

editor.Commands.add('tlb-delete', ed => {
	if (confirm('Sure?')) {
		const selected = ed.getSelected();
		selected && selected.destroy();
	}
});

@artf this works only for toolbar button, but when I hit "delete" on my keyboard it doesn't. How can I override this event?

Hi @Iceweex, unfortunately, at the moment, you can't. For the next release, I'll centralize those commands and will update also its event lifecycle, so in that case, you'll able to achieve the task in this way

	const commandName = 'core:component-delete';
    editor.on(`run:${commandName}:before`, (options) => {
	  console.log(`BEFORE ${commandName}`);
      if (!confirm('Are you sure')) {
        options.abort = 1; 
      }
    });
    editor.on(`run:${commandName}`, (deleted, options) => {
      console.log(`AFTER ${commandName}`, deleted);
    });
    editor.on(`abort:${commandName}`, (options) => {
      console.log(`ABORT ${commandName}`);
    });