Extending Core Block functionality without creating new block

Hi All,

I’m wondering if it’s possible to extend the functionality of a core block via a plugin or theme code, without creating a new block.

I have a very specific use-case: I want to extend the functionality of the core Query Loop block such that if multiple blocks are inserted in a post or page, they will never display any post that has already appeared on that same page.

Anyone know if this is possible?

Ideally, I’d like

An old “Classic” theme used on a site I manage had that function on the homepage, but it was hard-coded into the homepage PHP, template rather than achieved with individual Gutenberg blocks.

I realise I’ve bundled two questions together, which isn’t great etiquette I guess. Sorry about that.

Alex