Since it’s a Windows Store application: Windows 10
There is no combobox in the ScreenShots. The filters on the top are standard PopupMenu’s.
The Module list (on the very left) is a standard Listbox (of course with CellTextPaint and CellBackgroundPaint to customize the look). The white Listbox in the main content are is another standard Listbox (default look). And the main “grid” (the “Table” with the alternate row colors, the blue divider line, …) is… just a Canvas (but as you can guess: it does quite some things)
So basically: it’s all you can do yourself with Xojo - no Plugin Controls visible here. And no 3rd party components.
And while we’re at it: what you’re seeing is not a TabPanel. It’s a PagePanel, with a Canvas above it - it draws the “Tabs” and clicking will just change the PagePanel’s .Value.
But let’s don’t hijack this thread - if you’re curious to know more about how this-and-that has been done (how how it can/could be done), then feel free to create a new topic. And let this one be about showing Xojo built applications that are available on the Windows Store.