Thank god I found it! Hope this helps someone else:
Lock Widgets
Plasma 5.18 and above has hidden the “lock widgets” toggle. It’s very easy to enter “edit mode” with a long press. If you want to get the old locked mode behavior, run the following command:
qdbus org.kde.plasmashell /PlasmaShell evaluateScript 'lockCorona(!locked)'
If you want an easier way to toggle locking widgets in Plasma 5.18, install Win7ShowDesktop widget which has a “Lock Widgets” toggle in it’s right click menu.|