Open Opera: Launch the Opera browser.

Go to Settings:

Click the Opera menu button (three horizontal lines) in the top-right corner.
Select "Go to full browser settings" at the bottom of the dropdown menu.
Privacy and Security:

Scroll down to the "Privacy and security" section.
Click on "Site settings".
View Cookies and Site Data:

Under "Content", click on "Cookies and site data".
All Cookies and Site Data:

Click on "See all cookies and site data".
Find the Specific Cookie:

Use the search bar to find the site associated with the cookie you want to delete.
Delete the Specific Cookie:

Click on the site to expand the list of cookies.
Click the trash can icon next to the specific cookie you want to delete.
This will remove only the selected cookie without affecting other cookies.

What you can do is to load a page, click on the green shield in address bar, then in site settings and clean data to remove data for that site.