I have found the problem in 5 minutes (after posting)
“Tourner 7 fois sa langue dans sa bouche avant de parler” 🙄 😅
I had just to add a <div class=“column full-height”> directly under my q-card :
<!--
Forked from:
https://quasar.dev/vue-components/dialog#Example--Maximized
-->
<div id="q-app">
<div class="q-pa-md q-gutter-sm">
<q-btn label="Maximized" color="primary" @click="dialog = true"></q-btn>
<q-dialog
v-model="dialog"
persistent
:maximized="maximizedToggle"
transition-show="slide-up"
transition-hide="slide-down"
>
<q-card class="bg-primary text-black full-height">
<div class="column full-height">
<q-bar>
<q-space ></q-space>
<q-btn dense flat icon="minimize" @click="maximizedToggle = false" :disable="!maximizedToggle">
<q-tooltip v-if="maximizedToggle" content-class="bg-white text-primary">Minimize</q-tooltip>
</q-btn>
<q-btn dense flat icon="crop_square" @click="maximizedToggle = true" :disable="maximizedToggle">
<q-tooltip v-if="!maximizedToggle" content-class="bg-white text-primary">Maximize</q-tooltip>
</q-btn>
<q-btn dense flat icon="close" v-close-popup>
<q-tooltip content-class="bg-white text-primary">Close</q-tooltip>
</q-btn>
</q-bar>
<q-card-section class="col bg-white full-height">
<div class="column full-height">
<h2>Super Title</h2>
<q-scroll-area
class="col"
visible
>
<p v-for="index in 21" :key="index">
Lorem ipsum dolor sit amet consectetur adipisicing elit. Rerum repellendus sit voluptate voluptas eveniet porro. Rerum blanditiis perferendis totam, ea at omnis vel numquam exercitationem aut, natus minima, porro labore.
</p>
</q-scroll-area>
</div>
</div>
</q-card-section>
</q-card>
</q-dialog>
</div>
</div>
