For a multibranch pipeline we have a pipeline like this:

pipeline {
    agent none
    environment {
        RELEASE_BRANCH = 'master'
        // ...
    }
    triggers {
        cron(env.BRANCH_NAME == env.RELEASE_BRANCH ? '0 18 * * 7' : '')
    }
    // ...
}

The use case is to have the release branch rebuilt on a scheduled interval.
However, this doesn't work as env.RELEASE_BRANCH is not set when the trigger is evaluated. I suggest that the environment section is evaluated first of all sections or at least as one of the first, so that env variables can be used in other sections.