I'll give Germany credit insofar that it matters less than one would think. The only identifying documents that carry this information are passport and birth certificate. Social security number if you know how to read them.

You will still have to deal with a ton of bureaucratic overhead and little moments where this is disclosed. For instance, your health insurance (and doctors) will usually know (the marker, not that you're trans, i get endometrial cancer screening recommended to me) and start to bicker about non-standard healthcare (i.e. I can get my estradiol tested at my GP, but for testosterone I need to see an endocrinologist) and your social security / employer will know (I also have at least 3 aliased social security numbers at this point).

Pure gender marker changes absent a name change are a lot less common, so it's not exactly well known territory.