Use the Edit each ad (N) button, which appears right after you choose your creatives (or paste the Instagram links).

It opens a table with one row for each ad that will be created (each file in each ad set), showing:

  • the actual name the ad will get (same rule as the queue: AD##, complement, file name);
  • what will go out in main text, headline, website, UTMs and button: the shared field or, if it's empty, what will be inherited from the ads in that ad set ("Will inherit: ...").

To change something for just one ad, select Customize in the cell: the box is pre-filled with the value that would be used, so just edit it. Empty text removes the inherited value. Shift + click on Customize selects the whole column. Under Show, you can switch to Grouped by file, which is handy when a change applies to all ad sets at once (for example, only the name complement).