MS PowerPoint has three great ways to use custom shows: 

1. All the actual slides belonging to the custom can be hidden, so that they do
not show up during the main presentation. However, we can embed a link to the
custom show with any object. To start the custom show, just click on this object
in "slide show" mode. 

2. Place completely transparent objects (circles/rectangles) over different
parts of an image, and link them to different custom shows. This allows the
presenter to launch any desired custom show to explain different parts of the a
slide. 

For example, the slide has an image of a car. The presenter ha splaced
transparent shapes on different parts of the car and linked them to custom shows
that explain those parts. Depending upon questions from the audience, he would
click on the concerned part and launch the relevant custom slide show. 

3. After showing the custom slide show, the control is returned to the slide
that triggered the custom show.

***
But in Impress, none of these facilities are available. As a result, the custom
show is just a bunch of slides that Impress remembers as a set. THAT's IT! 

The only way to see custom shows is to select it from the 'Custom slide shows"
window and click "show". Thus we lose a lot of flexibility in presenting our ideas.

Desired: Provide all the three facilities outlined above for custom shows.