dependencies.edit: hover a bar and drag from the round handle at its end onto another bar to link them (finish-to-start). Click a link and press Delete to remove it. Keyboard: focus a task and press L, move to another task and press L again (again on a linked pair unlinks). Loops are refused. Ctrl/Cmd+Z undoes. dependencyCreate / dependencyDelete are cancelable and write dependsOn back to your data.
covered