My two cents
Specialized tools: These tools are specifically designed to build journey maps or service blueprints. Notable mentions are Smaply, TheyDo Custellence
My personal favourites are Notion to build very structured service blueprints and Miro, when I want to create service blueprints that are visually rich and appealing.
Service Blueprint resources
You can find all the Service Blueprint resources I've created here. This includes courses, templates and a library of external links and resources.