Assign Caption Times Window
Data|Captions|Assign Caption Times...
This window lets you assign caption times easily. Unlike the Caption list in the main window, the captions here are not sorted by time and need not have an assigned time until the dialog closes.
You can invoke this window either by the 'File|Import|Captions from Plain Text' command (for assigning times to the imported captions), or the 'Data|Captions|Assign Caption Times' command (for re-assigning times of the current captions).
To assign times, you will normally invoke this window, start the video preview and press F12 repeatedly while the video is playing, each time assigning a caption listed here to the current playhead time.
(This window is resizable and will stay on top of the main window).

Lists the captions. This list is read only. If a caption in this list has an assigned time, it will have a duplicate in the captions list in the main window, where you can modify the caption and the change will be reflected in this list.
Assign Time (F12)
Assigns the current playhead time to the selected caption and selects the next caption. You can assign the time after manually setting the playhead or while the video preview is playing. (If the preview is playing, the times assigned will be affected by the Playback latency value which you can change in the Preferences Dialog).
Clear Time
Clears the assigned time of the selected caption. Its duplicate in the main caption list will be deleted, and the caption will remain in this window without an assigned time.
Seek Time
Sets the playhead time to the assigned time of the selected caption. However, if the Video Preview window is open, the actual seeked time will most of the times be at the nearest key frame.
Clear All Times
Clears assigned times of all the captions listed.
Delete Caption
Deletes the selected caption. If the caption has an assigned time, its duplicate in the main caption list will also be deleted.
Lock Assigned Items
When selected, the captions with assigned times will be locked and protected from assigning a different time, clearing the time value and deletion. When a caption with assigned time code is selected, Assign Time (F12) will be changed to Step Over (F12), which lets you skip the caption.
Clicking OK closes the window. If there are captions left without times assigned, you will be prompted for confirmation, because you will lose those captions when you close: