Open a task → Dependencies → Add blocker. Pick any other task; the blocker must complete before this task can. Attempting to close a blocked task raises a gentle prompt instead of silently marking it done.
Waiting-On view collects every task blocked on a teammate. LemTask nudges you if a blocker sits untouched for 3+ days.
Why bother? Sequential work (design → dev → QA) stops surprising you. Cross-team hand-offs stop dropping.