Parameters in Power BI can be used for different purposes, one of the useful case to hold environment variable. For example, while you are building Power BI report source can be connected to DEV environment and as soon as report is ready to release you may want to connect the source from PRE-PROD/PROD environment. If you use parameter then it's become easy to handle.
How to create Parameter?
Open power query editor and then find Manage parameter and create New parameter as like below fig 1.0
Fig 1.0: Find New Parameter
My source is Salesforce and have three different environments, QA, UAT and PROD. At first provide the name of the parameter, e.g. my parameter name is: Environment, then choose Type as 'Text' and for Suggested values please choose 'List of values' as like below figure 2.0.
Fig 2.0: Creating parameter for different environment
Under List of values you will list down all your source environment and Default and Current value you need to set from those list of values. e.g. if would like to use QA environment then you need to choose the URL for QA for both default and current value.
Fig 3.0: Default and current value
As soon as you click 'OK' button then you are done. Yes, you are done with current value you set up; if you are connected for QA that's work fine. However, as soon as you change your environment from current value QA to UAT that works also fine if your source is database, but not for Salesforce source as expected.
What special about source as Salesforce?
After changing the source from QA to UAT and refresh the model, I got the below error:
Fig 3.0: Error after changing environment
How to fix it or What do you do after environment update for source as Salesforce ?
If you run into the same situation then please go to the power query editor then go to the source query as like below figure 4.0 for each table and then validate it by enter or the validation button (tick mark as like in the below figure). You will find error disappear. It's now can identity correct environment to connect.
Fig 4.0: Refresh data source
Update Environment from Power BI service:
Since you have created the parameter, so you can update the parameter value from Power BI service as well. Firstly login to the power BI portal and then find your published datasets as like below figure 5.0.
Fig 5.0: Settings under Datasets
And clicking ellipsis (...) you will find settings
Fig 6.0: Settings menu
Under settings you will see the parameter, where you can update the environment, you can replace UAT by PROD URL and click Apply which will connect to PROD environment and refresh your power BI model.