Often the user needs to select multiple objects from a slide. (Say, for
grouping, animating, etc).
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Often, it is very difficult to pick an object:
>> There may be nuimerous objects surrounding it.

>> There may be many overlapping objects (example: A mobile phone that shows
different messages on its screen. All the messages are stacked on the mobile's
screen, and animated to show one after the other.)

>> The object may have transparent background, and it is difficult to pick it
from the neighboring objects.
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Impress has no provision to let the user easily pick the object(s) of his choice.

Suggestion: 

The Navigator in Impress is very primitive (compared to Writer's Navigator). 
In its current form, it serves no purpose. (The "Slides" pane already shows all
slides, so the Navigator does not add any value at present.)

It should show a tree, as described below:
>> The top level nodes show slides in the presentation.
>> The second level nodes (under the slide nodes) show all objects.
>> If the objects are grouped, then the second level node should show the group;
and the third level nodes should show objects inside those group.