With the Swantide Workflow, you can synchronize an Opportunity's Picklist Field with a related Contact's Picklist Field through Opportunity Contact Roles.
For example, consider a 'Marketing Stage' Picklist Field present in both the Opportunity and Contact objects. If a Contact is designated as the Primary Opportunity Contact, the 'Marketing Stage' Picklist value on the Opportunity will automatically update to reflect the Primary Contact's corresponding value.
Note: you can only have 1 primary Opportunity Contact Role per opportunity.
When selecting my variables, I select both the Opportunity and Contact Picklist field in Scope as my variable input. I also enter a "Yes" or "No" variable option if I want the field to be updated based on the New Contact's Picklist Value in the event that I change who the "Primary" contact role member is on the Opportunity.
If I enter "Yes" the Picklist Field value on the Opportunity will update if the "IsPrimary" flag is updated on the Opportunity Contact Role.
If I enter "No", then the first time I set an Opportunity Contact Role as Primary Member then the value of the Contact will populate once on the Opportunity.
What this will look like in Salesforce after its been deployed from Salesforce:
Let's look at the following Opportunity as an Example. Currently, the Marketing Stage on the Opportunity is set to SQO and I have two Contact's related to the Opportunity via Opportunity Contact Roles.
At the present moment, "Andrew Tzikas" is marked as the "Primary" Contact Role and his Marketing Stage equals "SQO"
However, I have another Contact on the Opportunity "Mario Lopez" and his Marketing Stage is set to "SAO"
When I update "Mario Lopez" to be the Primary Contact Member, you will see that the Marketing Stage on the Opportunity will update to "SAO"
Note, in the Workflow Template itself, you have the Optionality if you would like to have the Picklist field in Scope change based on changes in the "Primary" Flag on the Opportunity Contact Role by typing "Yes" or "No"