I have version 8.96 Pro and I am able to change the duration of a whole sequence of image clips by clicking on the first clip, scrolling over to the last clip and holding down Shift while I click the last clip.
That selects all of them. Then I right click on any of the clips and choose Change Duration. The clip preview window opens and highlights the duration in seconds, below the preview. I type in the duration I want there and hit Enter. When I do that, all of the clips change duration to match my new duration I just entered.