"Freeze Row"/Pin Notes/Floating Banner

Use case or problem

Many applications have ways to pin text and data to the top of the current page/view that stays fixed as you scroll the page.

Here are some examples:

It would be extremely useful to have stuff like important tasks pinned to the top of a note (like a floating collapsible callout)

It could also be used to pin quotes, image banners, reminders, notifications, unread links (to Terms of Service/Licenses)

Proposed solution

see HTML - Fixed Header (see above, because “new users can only post 5 links”)

for displaying the data, see folding/collapsible callouts

  • a collapsible callout may be the best move for displaying pinned data, so that you can pin multiple items

Example implementations:

maybe we could make use of the ! at the beginning of a line?

I recommend a way to do a multiline pin as well. Something like this, so you could pin a list:

!!!
This is an important and blaring reminder-message-notification-thingy
- I want you to do these things, before touching my document
  - [ ] just don't touch it
  - [ ] please, I worked on this very hard
!!!

Maybe use it to replicate the excel freeze row feature:

  | col 1 name            | col 2 name
  | --------------------- | ----------
! | freeze up to this row | ....
  | ... a billion rows that makes it hard to track

Maybe add the ability to dynamically pin a row based on scroll position (there’s a few different variants in here:)

! Fixed Pinned Mesage that doesn't ever dissappear

...
... a million lines of markdown
...
!* Dynamically pinned message that only shows once you've scrolled past it

...
... a million lines of markdown
...
!!!*
Dynamically pinned message that replaces the previous dynamic one
- multiline dynamically, pinned message
!!!

...
... a million lines of markdown
...
!** Maybe even add support for dynamic sub-messages (like subheadings) that would display like this, once you've scrolled to this spot:

<!--
(top of viewport)
--------------------------------------------------------------------
Fixed Pinned Message that doesn't ever dissappear
--------------------------------------------------------------------
Dynamically pinned message that replaces the previous dynamic one... ▼
--------------------------------------------------------------------
  Maybe even add support for sub-messages like subheadings that would display like this, once you've scrolled to this spot:
--------------------------------------------------------------------
(where "▼" is the button to expand the multiline pinned message)
-->

I imagine you could make a custom callout type and a CSS snippet that makes it behave the way you want.