Hello,
Sorry to hear you are having issues. Need more information on your system. Please refer here: https://support.stardock.com/space/SHC/1387200583/Contacting+Stardock+About+Curtains+Issues

Thanks
Basj,
Stardock Community Assistant.

Is the issue only happen on Win11 Aero style? or any style? And if only Win11 Aero. Please post a link to where the theme I can download and verify it. Also, is the issue happen on any application maximized? or it happened on specific application?

Thank you,

Basj,
Stardock Community Assistant

Here is the link of the style : https://www.mediafire.com/file/fmj7vkyl7nzc4h6/WIN_11_Curtains.zip/file 

When downloaded go to : Win 11 Curtains-Win 11 Curtains- Win 11 Curtains-Win 11 Curtains

Then, you should see win11 dark aero.

Hi, it is when maximizing any application. Also I was not talking about that indicator, but the one beneath open taskbar icons

Ah, those thing. I wish you have post that screenshot in your first post. Those button was design by the author of the theme that way. You can change that taskbar button with one with a small dot when active. Refer screenshot below. That was taken directly from the theme and notice there are few buttons without that indicator oblong/dot thingy.

Thank you,

Basj,
Stardock Community Assistant

Refer screenshot below.

Thank you,

Basj,
Stardock Community Assistant

What do you mean?

Thank you,

Basj,
Stardock Community Assistant

You need to edit that piece of graphic using Graphics application such as Adobe Photoshop etc. Or, you can ask the author of that theme to mod it for you.

Thank you,

Basj,
Stardock Community Assistant

Put whatever that you wish to show up there. For example put a green oblong thingy instead. And choose a different color on those other ones.

Thank you,

Basj,
Stardock Community Assistant