Ability to open Excel Online in Edit mode by default or link to edit mode
Currently I need to click Open on Excel Online or Open Excel if I want to edit a workbook. If I have edit permissions, it should open in edit mode by default on Excel Online. At the very least we should be able to add a URL argument to allow it
Open in “Edit mode by default” is available for Excel files stored on SharePoint Online and OneDrive for Business.
Nick Rodgers commented
check your url if at the end it says "action=view" replace with "action=edit" and try that.
I hope that is what you are looking for.