Thanks for writing in.
Unfortunately, there’s no easy way to do this right now.
You might want to look at Allow plotly objects to use aggregated / precomputed statistics. · Issue #242 · plotly/plotly.js · GitHub for a possible workaround.
I’m thinking more and more box
traces should allow for pre-computed statistics (referencing Boxplot quartile seem's wrong). Unfortunately, it won’t be a high priority for us in the next few months. I’d recommend subscribing to Allow precomputed statistics input for box traces · Issue #1059 · plotly/plotly.js · GitHub for the latest info.