Compute and Resources are always shown. You can promote up to three more services to their own tabs from Tab layout.
Promoting a service
The promotable services are Storage, DNS, Billing, Databases and Kubernetes. Toggle up to three on. A promoted service only appears on connections whose provider actually supports it — otherwise its row shows "Not available on {provider}". Block storage, networking and firewalls always live inside the Resources hub rather than as tabs.
Global or per connection
By default your choice applies everywhere. Turn on Customize for this connection to give the active account its own tab set, which replaces the global default just for it.