Viewer and Aligner > sentence joining and splitting
Joining 
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 ()
Splitting in two 
To split a sentence, press . You will get a list of the words. Click on the word which should end the sentence, then press OK.
example
This will insert the words which follow (I need others etc.) into a new line below.
See also: Viewer & Aligner contents