Apple introduced a new productivity feature on iPadOS 15+ and macOS 12+ called Quick Note that aims to provide a quicker way to jot down things without you having to go in and out of the Notes app. When you activate it, the Notes app quickly opens and is available immediately.

You can bring up a floating Quick Note window on iPad using your finger or an Apple Pencil by swiping diagonally up from the bottom right corner of the screen. On Mac, Quick Note is implemented as a Hot Corner function. Pick a corner of the screen and move the cursor to that corner to trigger it.

Tap on the note brings up the virtual keyboard and you can begin typing. Quick Note also detects the app you are using and will show an Add Link button at the top of the editor window to insert a link to the current content.

When you are back on that content, a thumbnail of the note you saved before appears. Tap or click the preview to show your note. Likewise, selecting a previously added Quick Note link will open the corresponding content inside an app.

Additional information about Quick Note for iPad and Mac is available here:
MacRumours: How to Use Quick Note (iPadOS)
Macworld: How to use Quick Note (macOS)

Articles + supports to add Quick Note links to articles or annotations.

When reading an article, activate Quick Note to add a link back to the current content. If you select text and create a native annotation, the Add Link button allows to insert a reference to your note or highlight inside the app. To create a link for an existing annotation, tap the annotation and the Quick Note link button changes to the selected highlight.

Afterwards, if you come back to an article with an associated Quick Note, a thumbnail appears which lets you access your note. Or you can select a link you added to Quick Note to open the article or annotation inside Articles + again.

With Articles +, you can select text to create native annotations and export them from your library in text, markdown or json format.

At the moment, third-party apps can not directly add Quick Notes or have access to content inside Apple's Notes app. It is therefore not supported to add selected text or highlights to Quick Note and annotation export will not include your notes.