Even projects you did in the past as an architect use skills that are used in Service Design. So when you transition you can, for example in a portfolio, highlight what skills, technics, tools and mindsets that Service Designers use, you used in your previous practice.

In fact a lot of the design skills are the same between marketing, graphic design, UX design, product design, etc. Sometimes you just have to find how these things you do are called in another discipline to help people understand you already come with a lot of practice.

The team at Snook wrote an article called "Transitioning Careers — Advice from the Snook Service Design team" In the article you'll find tips from Natalia Riley who pivoted into service design from an academic background in psychology and a career in communications and marketing strategy. Here a summary of her tips:

Check out all the questions about Service Design as a career.