Dear Lissa,
Thanks for your your updates and kindness.
If the name parameter is extracted correctly from Parse JSON, you don't need to change it.
For your reference: Common ways to use a form in a flow - Power Automate | Microsoft Learn
items('Apply_to_each') is to get the values of fields in an array. It can't be changed.
I see that you use Apply to each 6 as the name of the Apply to each action. So you may use the formula like the following in your environment to see the result if the file name format is like upload file name+_your name+extension or upload file name+_your name+number+extension.
substring(items('Apply_to_each_6')?['name'],0,indexOf(items('Apply_to_each_6')?['name'],'_'))
substring(items('Apply_to_each_6')?['name'] , indexOf(items('Apply_to_each_6')?['name'],'.'), sub(length(items('Apply_to_each_6')?['name']),indexOf(items('Apply_to_each_6')?['name'],'.')))
Regarding "I advised that there is no available preview (these are image files) for the files that are added to OneDrive via the automation. If I manually add a file to the same folder, I am able to click on it and see a preview. If the file is added via the automation, I get a no available preview message.", based on my tests, the files created in the folder in OneDrive for Business or SharePoint Online by the flow can be previewed.
You can see the screenshots showing the result in my previous reply.
So what is the outcome at your side? Some related screenshots are appreciated.
Note: Remove any private information before uploading the screenshots.
Welcome to share any updates at your convenience.
Thank you for your effort and time.
Sincerely
Cliff | Microsoft Community Moderator