That is a Open file Window in Dolphin that is QT, I thought Waylnd only forced the button(s) to the top for GTK apps.
Hi - just to check, it looks like you’re in Firefox, rather than Dolphin, based on what’s highlighted in the task manager on your panel there.
In that case, it looks like your distribution hasn’t followed the KDE packaging guidelines for Firefox: Distributions/Packaging Recommendations - KDE Community Wiki
You can manually set Firefox to use the KDE file picker dialog by following the steps listed there:
Set
widget.use-xdg-desktop-portal.file-picker=1in about:config to make Firefox always use XDG portals for file pickers, which will make it use KDE’s file picker instead of the GTK one.