the opportunity is for china to be a signer of any armistice and a member on any arbitration board or similar adjudicating body for post war disputes between Russia and whoever their counterparty would be.
The aim is not to earn browny points. the political capital comes from more people having to secure your cooperation to get things they wanted done.
If europe has to secure chinese cooperation for mundane interaction with russia in eastern europe, china would have come our way ahead and it would be a huge set back for the US.
I think Chinese diplomats understand enough.
Both Russia and Ukraine still think they can win. Until one side has had enough, there is no point in trying to be peacemaker.
Russia doesn't really have an issue with Ukraine per se. Russia's beef is with NATO which is defacto controlled by the US.
From the Chinese point of view (along with others like India), NATO expansion has to stop. Yet for the past 3 months, the US has continued to push for NATO expansion to Ukraine, despite Russia making it very clear this is a red line. So what good is Chinese involvement at this point, unless the US/NATO publicly renounce expansion to Ukraine?
China also gains very little from a quick end to the Russia-Ukraine war. As soon as it ends, the US will go right back to trying to contain China.
And the longer the conflict goes on, the weaker the European economy become due to shortages and high prices, particularly in oil, gas and fertilisers. In addition, that the US is a petro-state which is based around burning cheap hydrocarbons like oil and gas. But these will become a lot more expensive the longer a conflict goes on.
In comparison, China is aiming to become an electro-state where energy consumption is based around the generation and storage of electricity. But an electro-state relies on manufacturing wind turbines, solar panels, dams, power plants etc to generate electricity which is used to power the economy with electric vehicles, electric trains etc.
So overall, at this time, I don't see any point in China trying to force a peace in Ukraine.
But in a few month's time, Russia/Ukraine/Europe/USA will be ready to sit down because of the pain caused by the war.