Every copy has a globally unique identifier and multiple copies can be changed in a single experiment, agnostic of channels. That way we only need to setup experiments on user level and as long as different channels are referring to the same experiment, consistent messaging will work out of the box for each copy across channels.

example: website_landing_page_title and email_subject_line can be part of the same experiment for a multi-channel experiment.

I'm curious to learn what kind of challenges you had in your past growth roles. It would be great to understand specific examples/workflows, and how you dealt with them.

One of the main ones that comes to mind relates to promotions. A good example is a fintech I worked at. We wanted to advertise specific offers to specific channels of customers, but we otherwise wanted communication with them to stay the same.

For example, we'd have the same opening email sequence, same retargeting, etc. for customers across channels but we'd want to have consistent messaging around offers (ie. "$1000 off when you sign up" vs. "first month free" kind of stuff). It was tricky because we didn't want to advertise the same offer to everyone, so we wanted to carefully segment who was getting which offer and keep it the same over a window of time.

Unfortunately we didn't have a perfect solution. The closest we came to it was to have an experiment ID tied to their user account. Then we had a system where we would define the different experiments (including messaging and promotions) with each experiment having an experiment ID. It was far from perfect but worked.