Quick capture is a small window that opens over whatever you are doing, takes a few lines and writes them into Grape. The app does not have to be open or focused.
Turning it on
Open Settings, go to the Shortcuts tab and switch quick capture on. It is off until you ask for it, because a global shortcut takes that key combination away from every other app on the machine.
The shortcut
The default is Cmd Shift Space on Mac and Ctrl Shift Space on Windows and Linux. The quick capture row is the one editable shortcut in the tab: click it and press the combination you want. If you record a combination the app already uses for something else, Grape accepts it but tells you which shortcut it takes over, because a global shortcut is answered before the window ever sees the key.
Writing a capture
Press the shortcut, type, and save. The first line becomes the note heading, so the capture reads as itself in the note list rather than as Untitled, and the rest of what you typed becomes the body with Markdown converted the same way the web clipper and the folder importer convert it. Dismiss the window and nothing is written.
Where captures land
Captures file into the folder every install already opens with, so they go somewhere familiar rather than into a folder invented for them. Change the destination on the same Shortcuts tab, and the folder is created if it does not exist yet.
After a capture
The note list catches up straight away, so the capture is there the next time you look at the app, and sync takes it to your other devices.
If the shortcut does nothing
Another app has probably claimed the same combination first. Record a different one in the Shortcuts tab. On macOS a fresh install may also need accessibility permission before a global shortcut is answered.