Adjusting caption timing
You can drag the edges of the subtitles to reposition them on the timeline - the waveform can help as a visual guide to the audio should that be needed.
Captions must not overlap; if two captions overlap, they will turn red to warn you. Drag the individual edges of the relevant caption on the timeline to reposition it so that there is no overlap (and the caption colour turns grey again)
Split captions / Creating new captions
Sometimes, a translated caption will contain more characters than the original language text, and go over the limit for a single caption. You can split the caption into two new caption. Place the cursor at the desired split point within the text, and click the 'split' button to the right. The caption will be split in two. It's likely you'll need to adjust the timings of the two new captions.
To create an entirely new caption, place the cursor at the end of the previous caption’s copy, and click the button. A new, empty caption will appear below.
To merge a caption with the caption after it, click the 'merge' button.
To delete a caption, click the 'delete' button at the far right.