I'm pretty confident in saying that no, you can't do this in the report itself. In that, you can't have an clickable item that makes it switch "on" and "off". What you could do, however, is add a parameter to your report of a Boolean type. This will appear as a tick box to the user in the report parameter pane. If they want the label(s) not displayed all they have to tick the box and rerun the report.
To set this up, you'll need to create said parameter (I'll call it HideLabel). Then, on each of your labels on your charts you want to be able to toggle you'll need to go to the Visibility property and set it to hide/display using an expression. The expression you need is:
This will tie the visibility to the tick box (True being Hide, and False being Display).
Excuse my typos and sometimes awful grammar. My fingers work faster than my brain does :-P
Please always remember to encapsulate your code in IFCode Markup. For example [code=sql] [/code]
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