As others have said, the CCP's clearly aware of the US election pressures and populist backlash against China that puts a lot of pressure on leaders to respond and one-up any Chinese response. So their strategy is to just match and never escalate, to try to delay as much as possible the speed of the decoupling while attempting to play the victim if possible (like with this consulate shutdown).

There's little to gain from attacking global markets outright. First of all it's difficult to do in a stealthy manner, and any overt moves are likely to hit their own fragile recovery efforts and economy. The "tail risks" and potential blowback of any such move against China are way too extreme. Secondly, it's likely China is aware that the best way to help Trump be re-elected right now is to show the American voter that China does NOT want him re-elected.