One of the features pioneered by Meta's Messenger app for Android is the chat head. Chat heads were floating windows that allowed users to send messages to their favorite contacts from any screen. Seeing the popularity of this feature as well as the growing use of the System Alert Window API upon which it relied on, Google introduced the Bubbles API as a purpose-built platform alternative, first as a developer preview in Android 10 and later available for all in Android 11.
Since its introduction, Google has not made any significant changes to the bubbles feature. However, it seems that could change in the future, as Google is working on a new "bubble bar" for large screen devices. This bubble bar feature may roll out in an upcoming Android 14 QPR or possibly in Android 15.
Currently, bubbles work the same way on large screen devices like tablets as they do on phones. That means they, by default, are anchored to the sides of the screen, as shown in the above image. That's not an ideal placement for large screen devices, though they can be later repositioned to be closer to the bottom.
In any case, Google wants to improve the bubbles UX on large screen devices, which is why they're working on the bubble bar. When the bubble bar is enabled, bubbles will be pinned to the bottom of the screen. The bar itself will be part of the taskbar and located at the bottom right, and users will be able to expand the bubble bar through a swipe up gesture. The bubble bar cannot be repositioned on screen like the stack of bubbles can on phones, but swiping up will reveal an expanded bubble view where the user can pick which bubble to open.
I put these details together based on my analysis of the code behind bubble bar, but I could be wrong on some details since I haven't gotten it to work yet. Code for this feature first appeared in Android 13 QPR2, but as of Android 14 Beta 5, the feature still does not work for me, even after enabling the requisite SystemUI flag.
It's likely the bubble bar feature is still being worked on, so we could see it land in Android 14 QPR1 (ie. the December 2023 Pixel Feature Drop) for the Pixel Tablet and Pixel Fold. I'll share a video of this feature as soon as I get it working.