You'll have to be a lot more specific with your question. Provide Operating System and Screenshots where possible.
Thank you for the answer Salah. It did not help...
I have uninstalled CS5.5 and re-installed again...BUT even this did not help.
And I do not recall doing anyting that blocked the "Toggle Visibility" feature.
Peter thank you.
Among the changes made on my laptop recently scaling the DPI was one of them, next to installing some software.
It is strange that only the Indesign 'tools and panels' was affected and not AI, PS and the rest of the applications in Adobe CS5.5 premium.
Anyhow, it is SOLVED!
Thanks Eugene Tyson, Salah Fadlabi & last but not least Peter Spier for your help.
I just encountered this problem with ID CS6 on Windows 7 after installing a new monitor and changing my display settings to a "custom" 110% . Using the Windows 7 125% display settings check box works fine, so it's not necessary to set it to the 100% default. The150% setting causes the same issue.
Just an FYI for anyone else who lands here with the same issue.