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Groups (option) is missing from Element of "Reset a Group/Popup" or "Display Data in Group/Pop"

I am trying to set up a workflow: when a dropdown input (X) changes to [something], reset another two dropdowns (Y & Z).

This is the element structure:
Repeating Group
Group Current Cell
Drop Down X
Group of Drown Down
Dropdown Y
Dropdown Z

So set up a workflow
WHEN dropdown X value changes,
STEP1 reset a group/popup

However, I do not see any of these groups in the element option.

Why is that? Is there any better way to achieve the function?