While it is perfectly valid to describe what they made as a designer or builder for LEGO, I do not believe they are allowed to use part of a trademark in a way

While it is perfectly valid to describe what they made as a designer or builder for LEGO, I do not believe they are allowed to use part of a trademark in a way that could be trademarkable itself, so basically good for everything but the name. But then again IANAL, and that is just how I understand the American law, and every country is different.