Regarding, Dataiku Scenario, How to control the Scenario steps using variable?

It's possible to do this using SQL but only if your dataset is stored in a technology that supports SQL. Therefore I would suggest using a metric for a more portable solution which will work for any dataset type. Follow these steps:

1. In the dataset where you have your true/false variable click on Metrics and then Edit Metrics and then enable Max on column statistics for your true/false column
2. Create a scenario step to "Compute metrics" and add the dataset that has the variable to it. You must give this step a name and you should not use spaces (let's call this step Compute_Metrics)
3. Next create a scenario step to "Define scenario variables"
4. On the Define scenario variables step toggle the "Evaluated variables" to ON
5. Then define a new variable (let's call it My_Column) with this formula:
   
   filter(parseJson(stepOutput_Compute_Metrics)['CT_TEST.my_dataset_NP']['computed'], x, x["metricId"]=="col_stats:MAX:my_column")[0].value
   
   You should replace CT_TEST by your Project ID, my_dataset with your dataset ID (leave the _NP) and my_column with your column name, case sensitive. Note that "Compute_Metrics" refers to the previous step name where you computed metrics for the dataset.
   
6. Finally in all your conditional steps (ie steps that should only run when variable = true) set "Run this Step" to "If condition is satisfied" and the condition to:
   
   My_Column == "true" && outcome != 'FAILED'

Sample execution with true value:

With false value:

You can use the same condition you use for the scenario step in the mail reporter. It works exactly in the same way.