In Gnome, timeout settings are made with commands. I couldn’t find it from the settings app.
(In standby mode, the screen darkens, the computer functions continues. In sleep mode, the computer puts itself to sleep slightly, the computer functions stops, wakes up with the press of a button on the keyboard.)
Commands along with descriptions:
Timeout for blanking the screen (seconds; 0 = never):
gsettings set org.gnome.desktop.session idle-delay 3600
Timeout for locking the screen after blanking (seconds; 0 = instant):
gsettings set org.gnome.desktop.screensaver lock-delay 0