The easiest way to join two sentences is simply to drag the one you want to move onto its neighbour above. Or select the lower of the two and press F4 or use the button ()
In this example, sentence 58 in Portuguese got represented as two sentences, 58 and 59, in English.
The best solution was press the Join down button.
Splitting in two
To split a sentence, press Split. You will get a list of the words. Click on the word which should end the sentence, then press OK.
This separates the words after mistaken into a new line below.
See also: Viewer & Aligner contents