It was removed because we needed to change directions on development and continuing to maintain it as well as build out the new implementation was untenable. It

It was removed because we needed to change directions on development and continuing to maintain it as well as build out the new implementation was untenable. It came out on Linux first because the Linux app was developed with it in mind, whereas on other platforms we were re-working existing systems to integrate with it. The former materialized quicker. - Ben, 1Password