I'm working on a project with some custom objects. On two of those objects (let's say A and B) I have a picklist which should contain the same options (one the B object the picklist is multi-select, on the A object it's regular). If an option is added to one picklist on object A, I want it to be added to B as well. Is it possible to do this (maybe using Apex)?
If by adding picklist values, you mean make available for selection automatically, i.e. metadata rather than data - then no, this isnt possible, unless you write some sort of external service which interrogates the metadata in Object A and applies it to Object B. Universal Picklists are a long standing idea.
If however you mean that on a record in Object A, a user selects a picklist value and you want the selected value to be applied to a related record in Object B, then yes this is possible with a trigger. (Or if A-B is Master Detail, with B as Master, you can use cross object workflow to update it)
- Just an update on Universal Picklists - Spring 16 for Pilot