There are a couple ways to do it that I've found. None of them is perfect for every situation I've encountered. I think that part of the reason why there's no clean way to do it is that there are so many specific things someone might want to do:

- If you want to just push cards to the back of the queue, but remember timings and history, there's a built-in command to do that.

- If you want to change the current interval of a card, but keep your history, there's also a built-in command for that.

- If you need to do the above in bulk, the "Reset Card Scheduling" plugin can make this a lot more convenient.

- If you really do want to completely reset a card, forget all history, etc., and treat it as a new card, there's the "Remove Card History" plugin.

Finally, when returning to old decks, I found I usually get the most mileage by leaving all that stuff alone and just suspending the whole thing, and then un-suspending them at a steady pace. I neglected my Kanji deck for months, and I used that approach to get myself back up to speed by doing the catch-up review in the original (RTK) order I originally learned them rather than based on Anki's priority.