The back of a card is usually the front's content ({{FrontSide}})
followed by the answer underneath. Anki's default template includes a divider
between the two, but it's easy to leave out when you're building a template from
scratch. Without one, the question and the answer read as a single block, which
makes it harder to tell at a glance which part is actually the answer.
A divider gives you a simple rule during review: "below the line = the answer." It sounds like a small thing, but across hundreds of cards in a review session that small difference adds up to noticeably less fatigue.
In ankieditor, select the Back side above the preview, click the element that should sit right above the divider (usually the question part) to select it, then click [➕ Divider] under Add Elements — the divider gets inserted right after it. Click it with nothing selected and it's added at the very bottom instead.
Click the divider you just added to adjust its line width. A newly added divider defaults to 100%, running edge to edge. If that feels too wide, try scaling it down to 60–80% — the line stays clearly visible while still doing its job as a boundary. Reposition it with [↑ Move up] / [↓ Move down], or remove it with [🗑 Delete].