@hemalathag8810 There is no such way OOTB currently. Building a DX component is certainly an option. But our product team is also looking at implementing this natively into the platform, no promises made - but could be an idea to weigh the implementation cost of adding a DX component vs waiting for native support.
Since Pega Constellation 25.1 does not natively support runtime theme toggling, you must build a custom DX Component placed in the portal header to handle the switch. This component will dynamically modify the application’s underlying CSS variables and design tokens on the document body when toggled. To ensure the selected theme persists across future sessions, save the user’s theme preference directly to a custom property on their Operator record. You can then load this saved preference during the login sequence using a thread-level Data Page to instantly apply the chosen mode. This direct approach successfully gives users full control over their visual workspace while working within the current platform architecture.
You are likely not seeing it because you have not configured your dark theme? I noticed when I went in, this was empty and I had to set it; and when it was empty at run time the icon was not there (which is expected outcome)
