Going with what Progressor brainstormed, perhaps a separate kind of tag that operates like a keyword but is not a keyword. It would have to visually appear distinctly separate from the keywords, probably on its own line and not using the same black boldface. Things like Quick, Swift, and No effect if New could carry their own terminology like "Effect" that doesn't count as a keyword for purposes of Witcher calculations (but are still accessible for other cards' effects like Don't be hasty).
It would make some cards more lengthy and it would remove Quick and Swift from the keyword pool, altering current balances, but it would allow for a truncation of "No effect if New" from several cards and allow for other similar truncations in the future.