@nelstevens I think this PR is also a great place to remove move_group. Playing with this package for few months, I realise users are not supposed to know the group ids, as they are assigned by dockview. When you start to move things around, you can easily lose track of those groups. With the new API, we have a group/panel mapping available with the proxy data, but this is more meant to be used by internal functions rather than by users. So we can just use move_group2 that works with panel IDs, where user have control over, and rename it to move_group. Do you have any concerns?

Leaving some days and discussing with @MikeJohnPage, we believe the approach is a bit too heavy on the R side, complex to maintain and feels a bit "off". We will go for another approach where checks are made by JS and relevant warning issued in the JS console and optionally as shiny notifications (shiny dev mode).

Layout helpers will be managed in another PR, as this one brings significant amount of changes.

Thanks again @nbenn and @MikeJohnPage for the feedback on this one.