On the conversion screen, open the "Custom Goals" tab at the bottom and click "Add Custom Goal" to see the following screen.
Check all the conversions you want to use and save them with an appropriate name.
Campaign Settings ①: Set a conversion goal
Select "Search Ads 360" in the "Conversion Goals" tab on the phone number data base campaign settings screen , select "Use campaign-specific goal" as shown above, and then select the custom goal you created in Account Settings ② and save it.
Campaign Settings ②: Adjust custom variables
Similarly, open the "Adjust Custom Variables" tab from the campaign settings screen and set it as follows.
Click the blue + button and select one conversion to use in the "Conversion Action" field on the following screen.
Adjust the values on the same screen and save them.
If you select Add, the value you enter on this screen will be added to the value you set in Account Settings ①.
If you select Multiply, the value you set in Account Settings ① will be multiplied by the value you enter on this screen.
If you select this setting, the value set in Account Settings ① will be ignored and the value entered on this screen will be used.
Repeat for all conversions you want to use.
Reference: Creating a custom conversion column (official help page)
Points to note when setting up
Please note that if you do not "Create a custom goal" and "Set a conversion goal" , the goals will not be used to adjust your campaign even if you have set them elsewhere.