Setting alt+shift as a way to switch between keyboard layouts doesn't work

[QA-EA]

In the new Keyboard settings, in the Layouts tab, the Options button is missing, which means there is no way to modify the shortcut to change the Keyboard layout to Alt+Shift (or any other option).
Trying to set it manually does not work.

The image is of older version of Mint.

The new one

[randomnoise]

You can click the "unassigned" button and then perform a keyboard button press combination to assign the keyboard shortcut in the "Shortcuts" section under the "Layouts" tab (it can be seen on your 2nd screenshot):

Hovering over the "unassigned" button will show you more information on how to assign the combo.

Completed shortcut assignment:

[QA-EA]

Already tried that; the combination of Alt+Shift does not work at all. In my opinion, the previous version was much better.