Hi Lucy LostWord,
Thank you for sharing the screenshot.
From what you described, I understand that when you open a window, it covers the taskbar instead of appearing in front of them.
I found several reports describing similar behavior, where open windows appear in front of the taskbar. However, I could not find an official Microsoft confirmation that this is a known Windows bug.
As a possible workaround, you can review this post from GitHub: RudeWindowFixer: fix Windows taskbar always-on-top issues which is designed to keep the Windows taskbar above open windows. Please note that this method recommends a third-party utility, so please review its GitHub page carefully and create a restore point before using it.
Optional method: If you are using NVIDIA’s In-Game Overlay, please temporarily disable it and check whether the taskbar behaves normally.
If the issue continues, press Windows key + R, type winver and press Enter. Please share the Windows version and OS build shown there. Also let me know whether the taskbar is hidden behind every window or only when opening pictures or browser tabs.