foundry/Data/systems/pf2e/templates/items/lore-sidebar.hbs

<div class="inventory-details">
    <div class="form-group">
        <label>{{localize "PF2E.ProficiencyLabel"}}</label>
        <select name="system.proficient.value" data-dtype="Number">
            {{#select data.proficient.value}}
                {{#each proficiencies as |label p|}}
                    <option value="{{p}}">{{localize label}}</option>
                {{/each}}
            {{/select}}
        </select>
    </div>
    <div class="form-group">{{localize "PF2E.LoreProficiencyDisclaimer"}}</div>
</div>