On a fresh install of the desktop app, the default dialogs folder is the ~/AppData/Local/Program/Mockoon folder, at least on Windows. This folder get wiped during each update. So, it's not a safe place to store any data (mock files).

We need to change the default folder, and maybe add a new settings field to setup the starting folder.

To reset the dialog previously selected folder (on Windows):
Remove the key in the registry:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedPidlMRU
(One of the entry is the one from Mockoon)