Default view mode/edit mode behavior for Word and Excel Online files

Onno van Ewyk I've replied to this blog post with a solution for this issue. Please see my reply below:

Hi All,

You can achieve setting the default to 'View" mode by using SharePoint Column Formatting.

Simply update your column (in my case I updated Name to keep the experience seamless) with the following json and your documents will now open in Preview instead of Edit:

{
   "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
   "elmType": "a",
   "txtContent": "@currentField",
   "attributes": {
      "target": "_blank",
      "href": "=if(indexOf([$ContentTypeId], '0x0120') >= 0, '?id=' + [$FileRef], @currentWeb + '/_layouts/15/Doc.aspx?sourcedoc='+ [$UniqueId] + '&action=View')"
   }
}

What this does is checks if the item is a folder and uses existing behavior to open the folder otherwise it will open the document in view mode.

Hope this helps anybody looking for a way to solve this issue!