The example application creates a new card from user text, all past cards stay on the page, and cards can be cleared with an additional button

permanate_cards.py

from datetime import datetime

from h2o_wave import main, app, Q, ui, on, handle_on
from loguru import logger


def on_startup():
    logger.info('http://localhost:10101')


@app('/', on_startup=on_startup)
async def serve(q: Q):
    logger.info(q.args)

    if not q.client.initialized:  # first time a tab comes this is app

        if not q.app.initialized:  # first time the app is ever used
            logger.info('Initializing the app for the first time')
            q.app.comments = []  # hold comments of all users
            q.app.initialized = True

        logger.info('Initializing the app for a new browser tab.')

        q.page['meta'] = ui.meta_card(
            box='',
            title='My Commenting App',
            layouts=[
                ui.layout(
                    breakpoint='xs',
                    width='1200px',
                    zones=[ui.zone('top'), ui.zone('comments', direction=ui.ZoneDirection.COLUMN)]
                )
            ]
        )

        q.page['comment_card'] = ui.form_card(
            box='top',
            items=[
                ui.textbox(name='user_comment', placeholder='Write some text here'),
                ui.buttons([
                    ui.button(name='comment_submit', label='Submit', primary=True),
                    ui.button(name='comments_update', label='Get Latest Comments', primary=False),
                ])
            ]
        )

        render_all_comments(q)
        q.client.initialized = True  # Document that this browser is setup

    else:  # if a tab is already active
        logger.info('Handling a user interaction')
        await handle_on(q)  # calls all "on" functions in order of q.args and stops after first match

    await q.page.save()  # Save changes to the screen


@on()
async def comment_submit(q: Q):
    logger.info('Rending user comment')

    comment = Comment(q.username, datetime.now(), q.args.user_comment)
    q.app.comments.append(comment)  # add to our shared-user list of all comments

    i = len(q.app.comments) - 1  # card number of this comment

    q.page[f'comment_{i}'] = ui.form_card(
        box=ui.box('comments', order=i),  # use -q.client.card_count if you want new comments on top
        items=[
            ui.text(f'{comment.date} - {comment.user} - {comment.comment}')
        ]
    )


@on()
async def comments_update(q: Q):
    logger.info('Re-printing all comments, unless there are new ones from other users')

    render_all_comments(q)


def render_all_comments(q: Q):
    logger.info('Adding any existing comments to the screen')
    for i in range(len(q.app.comments)):
        comment = q.app.comments[i]

        q.page[f'comment_{i}'] = ui.form_card(
            box=ui.box('comments', order=i),
            # use -q.client.card_count if you want new comments on top
            items=[
                ui.text(f'{comment.date} - {comment.user} - {comment.comment}')
            ]
        )


class Comment:

    def __init__(self, user: str, date: datetime, comment: str):
        self.user = user
        self.date = date
        self.comment = comment

Thanks Michelle! This is awesome help.