Hi Mahmoud,
If the button "More Intervals" is available depends on whether you're using the New Depreciation Engine or not. The button allows you to manage time-dependent depreciation terms. This is a feature only available with new Depreciation Engine. In old one, it was possible to only maintain one set of depreciation terms per area.
Also see topic 4.c in following note:
965032 - Differences between old and new depreciation calculation
The note also contains information how to check if new Depreciation Engine is active or not.
Best regards, Michael