Unable to add Lead Source in CRM Lists

Once Marketing Automation feature is enabled the option to add Lead Source on the Lead Source Lists will be disabled.

I. Temporarily disable Marketing Automation feature:

Note: May require i-alter

Navigate to Setup > Company > Enable Features > CRM tab > uncheck Marketing Automation

II. Create New Lead Source

1. Navigate to Setup > Sales > CRM Lists > New > select Lead Source
2. Enter value for Name. Example Web store 1 (or Web store 2, or Web store 3 etc..)
3. Click Save

III. Re-enable Marketing Automation feature