foundry/Data/systems/dnd5e/templates/advancement/parts/advancement-controls.hbs

<div class="form-group">
  <label>{{localize "DND5E.AdvancementCustomTitle"}}</label>
  <div class="form-fields">
    <input type="text" name="title" value="{{src.title}}" placeholder="{{default.title}}">
  </div>
</div>

<div class="form-group">
  <label>{{localize "DND5E.AdvancementCustomIcon"}}</label>
  <div class="form-fields">
    {{filePicker type="image" target="icon"}}
    <input type="text" name="icon" value="{{src.icon}}" placeholder="{{default.icon}}">
  </div>
</div>

{{#if showClassRestrictions}}
  <div class="form-group">
    <label>{{localize "DND5E.AdvancementClassRestriction"}}</label>
    <div class="form-fields">
      <select name="classRestriction">
        {{#select classRestriction}}
          <option value="">{{localize "DND5E.AdvancementClassRestrictionNone"}}</option>
          <option value="primary">{{localize "DND5E.AdvancementClassRestrictionPrimary"}}</option>
          <option value="secondary">{{localize "DND5E.AdvancementClassRestrictionSecondary"}}</option>
        {{/select}}
      </select>
    </div>
  </div>
{{/if}}

{{#if showLevelSelector}}
  <div class="form-group">
    <label>{{localize "DND5E.Level"}}</label>
    <div class="form-fields">
      <select name="level" data-dtype="Number">
        {{selectOptions levels selected=level}}
      </select>
    </div>
  </div>
{{/if}}