By using the Record URL Formula, you can generate a customized URL to display the portal with the desired menu for your users. Simply remove everything the &recordId parameter in the URL to create a working link.
For example, this is the formula that you can get from Record URL Formula:
'https://web.miniextensions.com/xyz?fieldId=abc&recordId=' & RECORD_ID()
After modification, it should look like this.
https://web.miniextensions.com/xyz?fieldId=abc