As the title says, ion-input-password-toggle does not show the placeholder for the associated input. Here is an example of the code:
<ion-input label="Password" type="password" label-placement="floating" fill="outline" formControlName="password" placeholder="Password" class="input-radius ion-margin-bottom">
<ion-input-password-toggle slot="end"></ion-input-password-toggle>
</ion-input>