What China needs to do is first stop the bleeding. Change the terms of trade with the US so that it doesn't accumulate mountains of USD that it can't offload except back to the US government. Russia has provided a beautifully simple solution to this dilemma - force payment in its domestic currency. China should follow this fine example and force the US to pay for Chinese goods in Chinese currency.
How would this work when RMB outside China is rarer than unicorns? Not China's problem... that's the beauty of it. That's the US's problem and it better solve it. Allow me to introduce you to one of my favourite scenes:
That's how it would work. Trade deficit? Fuck you, pay me in RMB. Capital controls? Fuck you, pay me in RMB. Financial collapse? Fuck you, pay me in RMB. Struck by lightning? Fuck you, pay me in RMB.
Once China does that, it can just sit on the US bonds it already does own and just wait for them to mature and use that cash to purchase tangible assets from anyone stupid enough to still accept USD.