You can hit t on your keyboard to add a task or click on the + icon at the upper right of your workspace.
Or click on the + icon at the far right of a task to add a sibling task.
You can hit Shift + Enter on your keyboard or click on the at the far right of a task to add a subtask.
You can hit Ctrl + Enter (or ⌘ + Enter for Mac) to edit a task name, or you can double click on the task name to edit it, and hit Ctrl + Enter (or ⌘ + Enter for Mac) to save.
Tip: If your task name is too long, you can hit Space to open up the detail panel to see the full task name.