The working solution:
{
"name": "acf/your-block",
"title": "Your Block",
"supports": {
"jsx": true,
"mode": false // disable mode switch in toolbar
},
"acf": {
"mode": "preview", // default mode (preview / edit / auto)
"blockVersion": 2
},
"align": "full"
}
Please remove the comments before copy & paste it as a JSON format doesn’t allow it.