When I enter the next line 789, the space before 456 disappears automatically. How can I keep the space before 456?
Use quote formatting (double `) on the space.
Better solution, as there is no visible change by default, but the leading/trailing space will still be preserved:
Is there any way to make this small gray square invisible, or change the background color of the small square to white?
Sure, here you go.
.quote {
background-color: transparent;
}
You also can use bold/italic format on the space
