One way to add alternates for items is to add "Alternate Sets" from the Catalog. This will add all items from the set to the quote and allow the customer to choose an item from the set.

If you don't want to use predefined Alternate Sets but still want to provide alternates for items within the quote, you can do so by adding alternate items within the quote. In the process, you will be creating temporary Alternate Sets within the quote, and you have the option to save these sets for future quotes.

To add alternate items, go to the side panel of the item and look for the "Alternate Items" tile. Here, click "Add client selectable item options" and this will open a modal to define the temporary alternate set.

The process to define the temporary Alternate Set is the same as how you would create a predefined set. Additionally, you can save the temporary set for future quotes.

Check out this article for more details about creating an Alternate Set.

In this example, we added an alternate TV for an existing TV and opted to save the temporary set for future quotes.

In the proposal, an item with alternates will show "View alternates" next to it. The process to select the alternate item is the same as that for selecting from the Alternate Set.

Check out this article for more details.