How can I change the date of my Non-O Visa extension while currently in Germany?

The only possible way to change the date would be if your passport expires in January, when you applied for an extension they would only give it until January.

Other than that the only other way is to leave Thailand without a re-entry permit and let your extension be cancelled by leaving, or to let your extension expire in May 2025 without applying for an extension.

If you already left with a re-entry permit when you went to Germany, you can't do anything because you will be stamped back in with that re-entry permit when you return to Thailand. The earliest chance you have to change it will be in 2025 by letting your extension expire and then starting over in October 2025 with a new 90 day non-O visa.

Theoretically if you got a new passport you could try entering with a new visa in October of this year, but they would still be able to see everything in the computer. But without the physical re-entry permit they likely would not stamp you back in on your previous extension.