It happens when you click on a link, than link is passed to the operating system to deliver.
So this question is in fact “incorrect” so an answer to it would be doubly so. At most we can ask where is the link written in the wiki.
I hope this helps.
To clarify then, does your key Objective remain as follows?
and the problem;
Tell me what you mean by “open in tiddlydesktop”.
Taking HELP TiddlyDesktop: Please, help me! into account my current hunch is your problem lies in the way you craft the link to local files, not the use of accented characters in the links. or alternatively what you are expecting to happen.
One way to explore this is in your browser see if you can browse your local file system. If so you will see the correct format in which to format the full path and filename. As before in chrome this worked typing/pasting in the address bar file://c:/TEMP/Cláudio.txt
if I copy the address bar I get file:///C:/TEMP/Cl%C3%A1udio.txt (note the ///)
to start just go to file:///C:/TEMP/ and browse the files there.
Now using this link file:///C:/TEMP/Cl%C3%A1udio.txt in a tiddler in a browser wiki or address bar opens the file in another tab.
In tiddlydesktop I added this to a tiddler;
file:///C:/TEMP/Cl%C3%A1udio.txt
<object data="file:///C:/TEMP/Cl%C3%A1udio.txt"></object>
The first creates a link that does not work for me;
The second successfully displays the content of file://c:/TEMP/Cláudio.txt
I hope this info helps you find your way.