Which version of Android is your Tab 6 Lite running? Odds are the Personal Dictionary menu option is just buried in a different location than on your S10e.
Just looking at a OnePlus phone running 12 in front of me, in Settings >> Keyboard & input method >> Personal dictionary. Samsung alters its Settings menu options in a lot of subtle ways so you might need to just look deeper in the Settings menu. Could be in a contextual menu, or some other type of sub-menu (i.e. in the upper or lower menu bar, there might be a gear icon, or three vertical dot icon, or three horizontal line icon).
Or just open the Settings menu and in the upper search bar do a search for 'dictionary' and that might show you where it's located.
Which keyboard app you using? There could also be a dictionary in the app's Settings/Options/Preferences menu.