change timing properties on only "next" buttons already on slides

Captivate 2019: we have hundreds of courses we have created in Captivate, each with almost 300 slides of information, and each slide with custom back and next buttons. This, however, allows the user to click next through each slide without viewing them in total if they desired. This worked for a long while, but no longer.

Because of this, we are needing to find a way to make it so the "next" button does not show up until the last second of each slide. Seems easy enough. But I am running into an issue trying to accomplish this with a mass action as opposed to slide by slide by slide. 

I can change the timing properties and drag the button to its desired spot, but this would take forever to do for each slide. So I can then click the option to apply to all buttons of this type. The problem there, though, is that then applies the same properties to the "back" buttons. We want the back buttons to stay as they are, there the entire slide so that users can seamlessly go back.

I can delete all of the next buttons, change the properties on the first, and then paste them back in across all of the slides. But then it pastes them all at the beginning of the timeline instead of the end, so we would have to go in slide by slide and manually drag them to where they need to be.

On top of that, it would be ideal if a user wanted to go back a couple slide that they would not then need to wait for a previously visited slide to finish before seeing the next button again.

The quiz questions have a skip button option which we can make active only once they've completed it the first time.

Am I missing some easy option? There has got to be a simpler solution to change properties on a single next button en masse. Any help is appreciated.

Arthur