Yes, you can extend your goal end date. You can do so by clicking on "Edit Goal" in Goal Details section.
Can I do mutliple investments against one goal?
Can I invest a lesser amount than the suggested amount?
Is there any penalty if I miss SIP payments towards my goal?
Can I stop SIPs midway before goal is completed?
Is there any penalty if I miss RD payments towards my goal?
Can I withdraw my savings before my goal is completed?
My goal got deleted automatically
How is the suggested amount to invest calculated?
How is OnTrack or OffTrack status decided for my goal?