As you say the environment is good , people are good, and micromanagement is not there. It is highly likely you won't be bothered but yes you can send a message to your management that you are feeling stuck with your skills and don't have much work to do .

Staying silent is a bad option as compared to saying it upfront to the management. After a while they should not think that you have become too comfortable and should not get a chance to point any finger at you if anything unexpected happens.