Item thumbnail value from item image field not website-image field

Hello everybody;
I need to make item thumbnail==item image not item website image as follows:
this is thumbnail field

I need to get its value from this field

I tried fetch from but not working
any help???

Fetch from only works when you’re fetching data from another doctype, not from the same record.

You need a custom script to do this.

Open the browser’s console and run this:

cur_frm.set_value('thubmnail', cur_frm.doc.website_image)

This will set the thumbnail to the uploaded file instead of the thumbnail image generated by the system. To make it applicable to all items, write the above piece of code as a custom script.