Does zeebe support partion rebalance while add new node into cluster?
currently not. But feel free to open a feature request on github with explaining your use case and needs.
and the clusterSize need to be config before start up, which mean the zeebe cluster can not scale horizontal dynamic? I mean current cluster have 3 brokers, I would like to add it to be 4 or 5 brokers without restarting the cluster
Correct, you cannot dynamically resize a Zeebe cluster at this point in time.
any plan for this ?
A quick search of GitHub returns this: https://github.com/zeebe-io/zeebe/issues/4391. Please add your use case and any comments on there.