If two annotations are adjacent and have the same length (for instance after creating regular annotations, see Section 2.9.8) and if the second annotation is empty, you can copy the value of the first annotation to the second. This is done by selecting the first annotation and pressing CTRL+SHIFT+D. Now the second annotation is selected and you can repeat the process to get a string of adjacent annotations with the same value.

An additional result of CTRL+SHIFT+D is that if there are annotations on another tier that have the same begin and end time as the annotations you are working on, and the second of those annotations is empty, then the value of the first annotation on that tier is also copied to the second annotation on that tier.