How could I use const in vue template?

If you expose them on your data, you are making them unnecessary reactive, as @mix3d mentioned…

A better approach is to add them into Vue object Reactivity in Depth:

<template>
      <div v-if="action === CREATE_ACTION">Something</div>
</template>

<script>
export default {
    created() {
        this.CREATE_ACTION = CREATE_ACTION;
        this.UPDATE_ACTION = UPDATE_ACTION;
    }
})
</script>