If I use CBs text analysis tool to see how many words in a txt file/anki deck are already in my anki decks by comparing it with the exported anki txt file, is there any good method to automatically suspend all the already known card in the new deck?

You could tag all your existing cards and then import the new list. Then use anki's tag duplicates function and filter the browser by "-tag:existing -tag:duplicate" and suspend them.

CB has another tool called word list duplicate remover that will compare two lists and sort by unique/duplicate words. You could use that tool to import only the unique words if you don't need the duplicates in your deck.

Thanks! I'll try that out.