To display a specific table when the portal or shared view is opened, you'll need to modify the Record URL formula. This will allow your portal or shared view to load a specific portal table, even if it is not the first in the list. You need to do the following:
Go to your portal or shared view tables section and copy the Record URL formula from the Create & Expand Records section of your table's settings.
Remove the record ID parameter from the URL:
Here is an example of the Record URL formula
'https://web.miniextensions.com/kLFbwMUXKgrsExF5jy7T?fieldId=fld8QDEJdKEyD7Tr3&recordId=' & RECORD_ID()
After removing the parameter, it should look like this
https://web.miniextensions.com/kLFbwMUXKgrsExF5jy7T?fieldId=fld8QDEJdKEyD7Tr3
If you want to limit the ability of your users to change the active table, you can hide the header and the tables and menu items of your portal or shared view from the Header & Profile section of the settings.
Using the resulting URL for each table will result in that specific table being displayed by default once the portal or shared view loads. This also works when your extension is embedded.