Looks like the new Bluetooth menu on Chrome OS 101 can now show the battery of each individual pixel bud (pretty sure it supports more headphones or will in the future) :
Android and Chrome OS preps headphone auto-switching - 9to5Google
How to Connect Bluetooth Headphones to Chromebook - Pair Bluetooth Earbuds Chromebook - YouTube
Sound not working on Acer Chromebook using chrome os flex installed through complete bios - ChromeOS Flex Community
How to connect AirPods to a Chromebook - Android Authority
Why Won't My Bluetooth Headphones Connect To My Chromebook ?
Chrome OS Starts Syncing Connected Bluetooth Devices - Chrome Story
Wireless Bluetooth® Stereo Headset | TARGUS
How to Connect & Set up Headphones on Chromebook (ChromeOS) - YouTube
How do I fix this problem...When I plug my earbuds in,the audio plays from the speakers,help. - Chromebook Community
Sound Not Working on Chromebook: 6 Fixes
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How to Connect Bluetooth Headphones to Chrome OS Flex (Bluetooth Pairing) - YouTube
How to Listen to TV With Your Headphones | PCMag
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Kabelloses Bluetooth-Stereo-Headset von Targus - Targus Europa