And you don’t have to do it that way. You can assign it in Tools -> Property Sets by right-clicking on the property set and selecting attach element to property set.
And, if you create the property set on the Properties tab of the element with Add Property Set button, the property set is automatically attached. That saves you from having to type in the properties except ones that are not in the default properties.
You probably know this, but to use a property set with an element, you also have to specify it in the tag:
[[!MySnippet@propertySetName? ¶m1=`hello`]]
If you don’t do that, the default properties (if any) will be used.