In the context of a user, you can add this metadata as a custom claim in tokens using an Action - Otherwise, you could just use the Management API /api/v2/clients/{id} endpoint.
A Post Login Action utilizing event.client.metadata might look something like:
exports.onExecutePostLogin = async (event, api) => {
// Check if a specific metadata field exists in the client's metadata
if (event.client.metadata && event.client.metadata.someSpecialFlag === 'true') {
// Perform a specific action if the flag is set to true
// For example, adding a custom claim to the ID token
api.idToken.setCustomClaim("https://example.com/special_user", true);
}
};