Does ES plan to allow changes to the "number of shard" when using snapshot recovery in the future?
Welcome to the community :)!
Some settings such as index.number_of_shards cannot be changed during the restore operation.
So no, you can't change the number of primary shards during a restore. You can change the number of replica shards as per the link above. To change the number of primary shards, after restore you'll have to do one of: