What tool is primarily used to view runtime information about a flow within the design environment?

The tool that is primarily used to view runtime information about a flow within the design environment is Execution Details. This feature provides critical insights into how a flow performs in real-time, allowing users to track the status of individual actions in the flow, see the outcome of each step, and identify any points of failure. Analyzing the execution details is essential for debugging and refining flows, as it highlights the flow's behavior during execution and shows the values of data pills used at various points.

In contrast, data pills are used within the flow to represent and manipulate data but do not provide insights into the flow's runtime performance. Subflows are reusable components within flows, serving to organize and modularize actions but again do not provide runtime tracking directly. Triggers initiate the flow when specific conditions are met, yet they don't provide the runtime analysis needed to monitor the flow's execution. Thus, Execution Details is the key tool specifically designed to observe and analyze the execution of flows.