To resolve effectively most of your display issues, in Remote Desktop Manager macOS, click on Window – Reset layout.
If it did not resolve your interface error, close the application and delete the layout files (.lyt).
Open Finder.
Click Go in the menu.
Select Go to folder.
Paste this path: ~/Library/Application Support.
Open the folder: com.devolutions.remotedesktopmanager or com.devolutions.remotedesktopmanager.free.
Locate and delete the RemoteDesktopManager.lyt or RemoteDesktopManagerFree.lyt file.
Launch Remote Desktop Manager macOS.