Hello, when customizing cabinets and wardrobes, the installation of adjustable-height countertops can refer to the following steps:

1. Right-click on the blank wall – select "All countertops"– "Countertop Installation", and first create two separate countertops at the respective high and low heights.
   
2. Press and hold Ctrl, then left-click to select both the high and low countertops, right-click on the countertop and select "Generate high and low countertop".
   
3. Use the left mouse button to click on the two lines representing the high and low countertops, select the side countertop texture according to the design requirements, and finally click to create.
   

You can refer to the following gif for guidance.