@hisham sharaf This is an expected behavior with the module as mentioned in the tooltip of the screen shot you added. Since you are using select columns in dataset module in between the dataset the clean missing module will not actually see the schema to list out the column names for selection. For example, if you use the clean missing data module after the dataset module it will be able to list the column names. Please see screen shot below:
For the above order, the clean missing data module will list the column names.
I hope this helps!!
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