Adding multiple dependencies
Sometimes more than one tasks needs to be completed before a "new task" begins.
In this case, open up the "new task" Properties Display
Switch to the Predecessors Tab (another word for dependencies).
Double-click on the 1st item in the grid  in the Name column and you'll see a combo box appear
graphic
From that list select the preceeding tasks, then you may double- click on following grid rows to add more preceeding tasks.
Note that the column to the right of the Name column, is called the Dependency Type... and JCV Gantt supports several different types of dependencies displays.