Any plans to advance it?

[zloirock]

The previous time this proposal was presented to TC39 5 years ago.

Are there any plans to advance it or is this proposal dead?

For me, at first, is interesting the keys composition part.

Now I'm cleaning core-js from dead proposals and I don't have much desire to remove such a useful feature -)

[michaelficarra]

The feeling I get from committee is that there is still appetite for continuing to pursue this proposal, but nobody has stepped up to do the work yet. The topic comes up pretty often.

[6XGate]

Thankfully the available polyfills work good enough to use this proposal for a hashcons implementation in JavaScript.