To logout one can click the top right power button in the WebUI. However having two dangerous buttons as neighbors is a design failure. I would recommend the developer to rethink its design and offer a better interface by relocating this logout button to somewhere safe.
Which version are you using? Because on my Electric eel install the logout button has already been moved
TrueNAS-SCALE-23.10.2
You are using TrueNAS SCALE 24.10 (Electric Eel)
Doesn’t it make you check a box and confirm for Shutdown? It does on Core