Finding characters not fitting Qt creator encoding scheme

Sometimes editing a file with Qt creator brings up the message: "Error: Could not decode "blablobli" with "UTF-8" encoding. Editing not possible."

One can select another encoding scheme and editing is possible. Also the scheme does not change the "wrong" character while storing. All is fine.

However, it would be handy to have help to find the location of the characters causing the problem. Currently, the characters are marked through a special "character" as a rhombus with a question mark when the file cannot be edited.
When a translation is selected and the file can be edited, these marks are gone. Also a find with regex does not support finding these "wrong" characters and their location.

Therefore, editing for removal of those issues is not supported within Qt creator. Either one uses trial and error or other tools for changing.