You can use Joplin's Swap line down and Swap line up features for this.
Desktop:
- Use Alt+Up to swap the current line up.
- Use Alt+Down to swap the current line down.
- If you want to use a different key combination for either shortcut, you can change it in
Tools>Options>Keyboard Shortcuts.
Mobile:
- While editing a note, swipe left on the bottom toolbar until the rightmost button (with the gears icon) is visible.
- Tap that button, scroll down the list until you see
Swap line downandSwap line upcheckboxes. - Tap both checkboxes to make those buttons show in your toolbar.
- Press the top-right
Xclose button to return to the editor. - Swipe right until both swap buttons are visible, then tap them as needed.