I just tested how the v3 block changes will impact our blocks. In doing so I see that the acf>mode value in blocks.json is no longer being respected, not for v2 blocks either (contrary to what is written in the release posts which say that v2 will keep working like it did). We usually use mode:preview, and force the users to use the fields on the side. But even with v2 blocks, you can now switch to the edit mode in the UI. I can somewhat understand that in v3 this won't be an option – because no edit mode will be available anymore. Some feedback about the edit button – might I suggest removing the edit button and instead adding a "expand" icon in the block sidepanel, which brings up the larger panel with block fields. Perhaps the "mode" needs to be thought out from scratch. Just throwing an example out there field_position: auto (both), sidebar, full auto – gives the current solution (though I would recommend adding a expand button) sidebar – fields are only shown in sidebar, full – fields are only visible in the expanded panel, sidebar shows a short text and button for accessing these. Why though? sidebar: if fields are simple, you don't really need the additional view full: if you have large repeaters, flexible content, nested fields, etc. those will just look very cluttered in the sidebar