I want to add a new palette apart from the existing one to show conditionally some model information. Any help in that direction is highly appreciated.
i tried overlays but that is always connected to some element and move with element inside editor.
If I understand you correctly, you want to adjust the palette contents. Please have a look at the custom controls example and come back here if you have any follow-up questions.
Then I’d suggest you take inspiration from the existing palette and based on that you create your own. (I wouldn’t use the overlays feature for that as its purpose is to show HTML next to a selected diagram shape).