Can we selectively have different objects in different modes using Fluid Boxes?

In the instance I'm referencing I wanted to have two versions of a slide that was showing the screen of a smartphone. On the desktop version of the slide, I designed it to appear on a mockup of a smartphone to illustrate that this view was what the end user would see on a smartphone. In the case where the learner was viewing the training on a smartphone, I didn't want to show a picture of a smartphone on a smartphone so I made a version fo the slide where the screen filled the screen. I used something similar to the following advanced action to make it work. I didn't really see it as overkill as the results were really nice and the client appreciated the small but extra effort.

What you are pointing out is the reason why I label responsive projects with Breakpoints full responsive, whereas Fluid Bpxes projects are sort of hybrid between a non-responsive project published as scalable HTML5. Not fully responsive because you cannot replace items for lower browser resolutions, only make them optional.

Have a look at my comparison:

Fluid Boxes Or Breakpoint Views? - Captivate blog

So you can do one or more of several things to customize the view for different devices. Unlike breakpoint style responsive design there is no way to move an object off the stage for a certain device. You can set an object or a child level fluid box to be optional. When the screen size drops below a certain percentage which you set on the parent fluid wrap options that object or child level fluid box disappears. Here is an example where the optional content (the cutout character) disappears when there isn't enough space to display it.

One alternative to this is to use advanced actions and look at the system variable cpInfoMobileOS and have it navigate to different versions of the same slide depending on the value of cpinfoMobileOS.

Desktop = 0

iOS = 1

Android = 2