The way to access more things in the Smart Stack is to take advantage of the fact that one of the apps in the multi-function widget can be the Shortcut app. Many old complications and apps can easily be embedded in Shortcuts. So, you create those Shortcuts and order the Apple Watch Shortcuts so that your favorites are at the top.
In many cases, the Shortcut can be a one-step action of Open [App]. You can do this for apps with an iPhone and Apple Watch presence. If you use a particular command in the app, it may be a Shortcut action. Once you create the Shortcut, go to the Info panel for Shortcut and check off the Apple Watch option.
My situation was even more complex than Dave K’s. I had a full Dock of applications in addition to using a fully loaded Infograph watch face (8 complications). For Watch OS 10, I wanted to use the no-complication Snoopy watch face. After evaluating my priorities, I ended up with these Smart Stack Widgets:
Multi-function (pinned)
Alarm (pinned)
Noise
Medications
Calendar (Your Schedule)
Heart Analyzer (Recent Heart Rate)
Medications
Weather (Conditions)
Mindfulness
In the Multi-Function widget, I have the basic Timer, Workout app, and Shortcut app. When I open the Shortcuts app, the top 3 are visible, with a button to show the rest. My top 3 are a combo shortcut related to activating sleep, Open Shazam, and Open Maps. The latter 2 are one-action shortcuts that perform those actions. Below them, I have other Watch shortcuts in priority order.