Difference in landscape height for multiple landscapes

i am trying to sculpt multiple landscapes to optimize the game and the problem is the difference in heights causes cracks such as below

In case you’re still looking for the answer, using World Composition will allow you to edit to levels together.
In World Settings, check Enable Work Composition. Open levels window (Window > Levels) and click on the little white checkmark/box icon by the magnifying glass. When the WC window opens, right click on one level and select “Add Adjacent Landscape Level”.

That technique only works for a non pre-created landscape tho.