I changed max_optimization_threads from null to 2. using this command in qdrant dashboard console:

PATCH /collections/test
{
    "optimizers_config": {
        "max_optimization_threads": 2
    }
}

when run this to set it null again the value doesn't change (without any error or complain):

PATCH /collections/test
{
    "optimizers_config": {
        "max_optimization_threads": null
    }
}

qdrant version : 1.12.1