I know there are some feature requests that address this, but am wondering if there are any workarounds.
The basic use case: In SFDC campaigns, we have a custom picklist field named "Category" that lets us select values like "Acquisition" and "Nurture", or a picklist "Theme" field that let's us pick values like "Gartner MQ 2017" or "Competitive Discount". What we'd like to do is create smartlists where the criteria is "Member of any Campaign where Theme = Gartner MQ 2017". It's a shame you can't do much with filters or constraints for SFDC campaigns. These values are unique to the campaigns and don't have analogs in the Marketo Smart Programs that they may be tied to.
Unfortunately you can't do that.
The workaround would be coming up with a naming convention for your SFDC campaigns and then using the SFDC campaign name contains filter.