Grab anywhere on the block
Drag an unfinished productive block. The point you grab stays under the pointer: grabbing the middle and dropping at 14:30 positions the block's beginning earlier by the same visible offset. Placement snaps to 15 minutes. Day and Week map through the displayed hours; Month and Quarter map through calendar days, including compressed weekends. Earlier/later work can be revealed with Show full day.
The outlined preview shows the requested position. The scheduler decides the feasible allocation after checking calendars, higher-priority work and prerequisites. The proposal remains temporary until you review and apply it. Discard restores the live plan.
Move
Plain drag reschedules the existing work. Moving a single-person block to another row reassigns that work; it does not add an assignment. A separate outstanding contribution cannot silently transfer to another person. Move a shared independent block horizontally to change that contributor's start; simultaneous horizontal moves reschedule the group. Replace or remove shared contributors in the stage editor. Completed history and waiting stages cannot be dragged.
Shift: add independent contributor
Hold Shift while dropping onto another active resource. The original contributor remains and the new person contributes to the same stage. The new contribution has its own requested start, so the original person's schedule need not move. Repeat to add a third contributor. The effort remains the existing stage effort per contributor, unless an individual outstanding contribution already exists; it is not automatically divided between people.
Ctrl: add simultaneous contributor
Hold Ctrl while dropping onto another resource. Everyone remains assigned to one stage and works in matching intervals. CYJ finds common availability at or after the requested start, respecting priorities, human calendars, breaks and existing commitments. A continuous agent does not make a human available overnight. Repeat Ctrl-drag to add another simultaneous contributor.
Mode and failure feedback
The preview says Move, + Independent or + Simultaneous and uses different border shapes. Press or release Shift/Ctrl during the drag to change intent; Ctrl takes precedence if both are held. One shared stage must use one mode. You cannot Shift-add to an already simultaneous stage or Ctrl-add to an independent shared stage. Model genuinely different work as separate stages with prerequisites.
An impossible placement displays an explanation and leaves the previous proposal and live data intact. Some common windows can be later than the drop preview; review the recalculated plan before applying. Target and hard-deadline risks are shown, rather than bypassed by dragging. See What If and collaboration.
Modifier gestures are for desktop. On touch devices use the existing stage editor and planning panel; no mobile modifier gesture is required.