Can I trade in my MacBook Air if it’s on activation lock?

No. The device must be unlocked and restored for trade in. Apple will return an Activation Locked device sent in for trade-in.

Link-> What to do before you sell, give away, or trade in your Mac - Apple Support

You will need to recover your account then. It cannot be traded in with Activation Lock.

Link-> If you forgot your Apple ID email address or phone number - Apple Support

Link-> If you forgot your Apple ID password - Apple Support

You can’t trade in with an activation lock. Apple cannot unlock it so it is useless for them and you.