There may be something amiss, or being overlooked. A second channel can be added. Press the Add button and name it. 
Subtitle default length is set under the OPTIONS | EDITING menu.
In the subtitle configuration box, position the cursor where you want each title, type it, then click the green + ADD.
Or, prior to pressing ADD, click the "Go To End" button under the preview window, then click ADD. The sub will be placed immediately following the one before

To change IN/OUT times, select a subtitle, then click in the time windows below the preview screen and adjust the times.