Python supports "/" and "\" separators on Windows.
So in IDLE, the path shown sometimes is:
D:\xxx\xxx
Sometimes is:
D:/xxx/xxx

That isn't right.

This complaint is way too vague to work with.  And for anything specific, it is almost certainly misdirected as the behavior is almost certainly not an IDLE issue.  If your code, which is executed by python, not by IDLE, prints a path, IDLE displays it as is, which should be the same as printed by the same code executed directly by python.exe, without IDLE involved.  If IDLE displays a path as a result of other user actions, it displays the strings returned by os.path, or maybe someday by pathlib.

If you have specific complaints about the behavior of os.path, pathlib, or other stdlib functions, you could open a new issue.  But I strongly suggest posting to python-list first, as these functions are mostly old and their well-discussed behavior unlikely to be seen as a bug by the developers who maintain them.

If after posting to python-list (which I read), there appears to be a specific issue with IDLE, this could be re-opened.