how can I use the dev or branch target in DBT for a dagster cloud deployment?

It's not well surfaced in the guides, but when you load assets from DBT, you define a DBT resource, and in this resource, you can pick the DBT target to be used.

resources = {
    "dbt": dbt_cli_resource.configured(
        {
            "project_dir": DBT_PROJECT_PATH,
            "profiles_dir": DBT_PROFILES,
            "target": MY_TARGET
        },
    ),
}

defs = Definitions(assets=load_assets_from_modules([assets]), resources=resources)

Agree with Nicolas! There's an example of this in action here: https://github.com/dagster-io/hooli-data-eng-pipelines/blob/master/hooli_data_eng/definitions.py#L99-L156

I'm suggesting a docs change about that https://github.com/dagster-io/dagster/pull/13361