If you already have an existing project, ViSi Genie might be the best for you.
This allows you to design a user interface and control it using your main/host controller without the need to program the display.
However, keep in mind that ViSi Genie have some limitations since it was designed to follow the most common behavior expected for each widget.
If you want or need a custom behavior, you can add custom code with ViSi Genie Magic which is available for the PRO version of the IDE. Keep in mind that you need a good understanding of program flow and 4DGL to efficiently utilize ViSi Genie Magic.
If you need full control of the display, you can use Designer or ViSi.