This action tag is used to set an attribute of Custom Element. It’s rare case that we need to set an attribute. But in Realm it’s possible to do that.
<my-element>
from the devtools, you will see the owner
attribute will changed once you click the button.
<custom-element name="my-element">
<element-attr name="owner" type="string">No Owner</element-attr>
<element-flow>
<trigger-event click="Button">
<set-attr name="owner" value="New Owner"></set-attr>
</trigger-event>
</element-flow>
<template>
<slot name="@owner"></slot>
<button ref="Button">Click me!</button>
</template>
</custom-element>
<my-element></my-element>
<br />
<my-element owner="R. Pracutian"></my-element>