Hi @CAIANI, ALBERTO
Welcome to our forum!
Based on my research, the position of archive you mentioned in the picture can be moved around as you like by dragging and dropping.
The default location of local .pst files is C:\Users\<Your Username>\AppData\Local\Microsoft\Outlook\,
you may find it by going to File>Account Settings>Account Settings>Click on the Data Files tab.>Select the .pst file you want to locate and click Open File Location.
As for "error 0x8004060C, Archive has reached maximum storage capacity", it seems PST file exceeds its size limit, you may refer to the steps Katherine Yu MSFT mentioned to reduce it:
More information: Outlook Error code 0x8004060C - Microsoft Community
If this doesn’t help, considering data file corruption, it is proposed that you create a new profile, re-add your account to the new profile and check if the same error still occurs.
Hope it helps!
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