Slide transitions

I just started using Captivate 2019 and discovered that there isn't an option for slide transition!  But I discovered that there is a still an option to fade in and out for objects.  So I'm adding white squares over my slides and then using the fade out option.  When published, the visual experience is the same as using slide transition.  The only downside is that you can't see the actual slide in the source file after you add the shape over it. My plan is to do that last, right before I publish.

Yes you can. You have to select your slide then press on "Timing" (next to properties top right) then select from the drop down options. There doesn't seem to be any control of the length of the transition eg I wanted my fade to be 5 seconds but I can't seem to control that anywhere.

Moderator: you cannot use slide transitions in any responsive project or in a non-responsive project published to HTML. Check the HTML Tracker

The info in this answer is irrelevant, only valid for SWF output.

You are working on a responsive project, which doesn't support slide transitions.  Was that tutorial for a normal project?

Slide transitions are a SWF (shockwave flash) animation. As such, they are not available for responsive design projects due to being exclusively HTML5 format. I suggest looking into HTML5 animations and using object effect animations to try and mimic what you want your slides to do. Be sure to go to Project -> HTML5 tracker to see if there is any SWF conflict.