I will say that the best way is not to change the action to minimize. Just live it as it is. Instead, if you look at this Navigate to the "Behavior" tab and select "Minimize" in "Click action". Next to the click to action you will see a gear icon.
A new window should popup (Customize middle-click behavior) there you can see on the first option that Shift+Click already is set to minimize the window. So you can leave all default and when you want to minimize the do Shift+Click.
I recommend this because there are other post where people gets annoyed with the result after they change this behavior and then want to reverse it because this does not work properly when you have multiple windows open.
Here is a screenshot of the screen that I am referring to:https://i.stack.imgur.com/LqHzs.jpg
Step one Click on the settings next to the on button
Step two click on the Behavior tab
Step three click on the gear icon next to the Cycle through windows
Step four look at the first option that indicates to use Shift+Click
Using this will allow you to get the functionality you desire without having the issue that other are complaining about when it come to multiple browser windows open.
Here is one of the comments that I found around the internet of issues when changing that behavior How to turn off on click minimize on dock option on Ubuntu 18.04?