Galaxy Tab S4: Multitask from the Recent Apps Screen
Navigate to Apps screen > Tap More Options. > Tap Card view > Tap Multi Window > Tap the second app (example, touch Internet) > Tap and hold the area containing the desired text > Adjust the selected area by touching and dragging the anchors at either end of the selected text > Tap Copy > Tap Create Note > Tap and hold the Notes field > Tap PASTE > Tap SAVE.
Pictorial representation of the above settings are as follows:
Note: Multi Window supported apps are displayed on a split screen, running at the same time. You can switch between the apps, adjust the size of their display on the screen, and copy information from one app to the other.