Shopify caps every section at fifty blocks, and in the Service menu both Category and Service blocks count. Past fifty, the editor stops offering Add block.
Two ways round it:
- A category page per group. Give each service category its own page from the service-category template, with the full menu for that category. The services page then lists the headline services and links down. This is how the demo is built, and it is better for search engines too, because each category gets a page and a title of its own.
- A second section. Add another Service menu section to the same page. Each section is its own fifty.
See Service menu section and Category pages.