You are looking for andThen operator.
Returns a Completable that first runs this Completable and then the other completable.
firstCompletable
.andThen(secondCompletable)
In general, this operator is a “replacement” for a flatMap on Completable:
Completable andThen(CompletableSource next)
<T> Maybe<T> andThen(MaybeSource<T> next)
<T> Observable<T> andThen(ObservableSource<T> next)
<T> Flowable<T> andThen(Publisher<T> next)
<T> Single<T> andThen(SingleSource<T> next)