Hi
Subtitles are related to the timeline on a time basis only. They are not clip related and so can be placed for the duration of multiple clips. Adding, editing or deleting clips does not alter the subtitle position relative to the timeline. A subtitle set to appear at 30 seconds from the start will always appear 30 seconds from the start irrespective of the clip it plays over. if you want to keep them correctly positioned you will need to reset the START/STOP times for the particular subtitle as well as all the others that follow it. You can do this as follows...Open the subtitle entry window, click the relevant subtitle and adjust the START/END positions. The position of the text is shown by a highlighted section of the thumbnails. The list will show the new values. Currently there is not a batch move option.
It's a mistake to add subtitles before the editing is complete and they are best left until the end. The alternative and which has more controls is to use the Add text feature.
Nat