How to create a new column in an existing Layer
- Select the layer in the Layer Stack
- Choose Layer > Add Column (a new column named "New Column" shows up in the data pane)
- It is a good idea to open up the Layer Info window (Window > Show Layer Info) and change the name, and possibly the type of the column
To enter data, go do the data pane and double-click on the cell that you want to edit, the blinking cursor should appear and allow you to change the data.
At this time, there's no way to quickly enter a column of data, so you'll need to double-click on each cell to start editing and then you can hit tab, return, or click on another cell to finish editing the data.