Reckon parallel release versioning

Question

We've been using reckon for semantic versioning in gradle:

plugins {
    id("org.ajoberstar.reckon.settings") version "0.18.0"
}

extensions.configure<org.ajoberstar.reckon.gradle.ReckonExtension> {
    setDefaultInferredScope("patch")
    stages("beta", "rc", "final")
    setScopeCalc(calcScopeFromProp().or(calcScopeFromCommitMessages()))
    setStageCalc(calcStageFromProp())
}

which has been working well as it dutifully calculates the next git tag in gradle.

However, we'd like to maintain 2 releases while we're upgrading to a new micronaut version which seems possible using release branches such as release/4.0.x, but I haven't gotten it working nor can I find an example.