If you have a Sharepoint site like the following:
https://sharepoint.contoso.net/sites/{sitename}/Shared%20Documents/{folder}/{subfolder}
It is possible to open this up in Windows Explorer by changing the link to the following:
\\sharepoint.contoso.net@SSL\DavWWWRoot\sites\{sitename}\Shared Documents\{folder}\{subfolder}\
Click "Return to classic SharePoint".
In Sharepoint Classic, copy the simplified sharepoint address (i.e. without the "RootFolder=?"), by clicking the little mobile phone icon:
ALTERNATIVE METHOD: You can also get the URL by copying the path (These paths will automatically redirect even the file is moved):
2. In the Edge toolbar, click the three dots and then "Reload in Internet Explorer Mode". Ignore the "it's time to upgrade" web page that appears. This is to force the browser to bypass the Trusted Sites. You may need to do this step every time you reboot.
3. Go to https://onlinetexttools.com/url-decode-text and paste the URL. Copy the result to clipboard.
4. Open up Notepad.
5. Paste the URL into Notepad.
6. Change the URL so it looks like the following (i.e. replace the italics with your domain and path, change the forward slashes to back slashes, add DavWWWRoot before sites):
\\sharepoint.contoso.net@SSL\DavWWWRoot\sites\sitename\Shared Documents\folder\subfolder\
7. Copy this URL to clipboard.
8. Launch File Explorer by Win + E.
9. Right-click on This PC and select Map network drive.
10. Map the network drive as follows:
11. If you ticked "Connect using different credentials, then enter your username and password. For your username, ensure that you add your domain (e.g. contoso_users\username or username@contoso.com).
12. If the network drive doesn't appear, but you don't receive any error messages, then log out and log back in.
Ensure you reload the site in Internet Explorer mode before you try to connect, or it will say there's an authentication error. Internet Explorer inserts a cookie for the authentication that allows Sharepoint to connect as WebDav without re-authenticating. You will need to do this every time you reboot, as it is no longer possible to tick the "remember me" checkbox in Internet Explorer since an "upgrade me" message appears instead.
When mapping the drive, ensure that you use the full URL path - it needs the folder that you have permissions for access. Otherwise it will map the drive, but then an error will appear saying you don't have permissions.
Ensure that the website is in your Trusted Zones:
Start > type "Internet Options" > Security > Trusted Sites > Sites > Add this website to the zone: {enter website with https://} > Add > Close > Custom Level > User Authentication > Logon > Automatic logon with current user name and password > OK > OK.
If you still cannot connect, please see the troubleshooting steps in the links below,