Hello Andy L_769 and welcome to the Microsoft Community!
Based on your feedback, you want to disable Tablet Mode!
I'd like to check with you to see what brand of external monitor you are using for Tablet Mode.
What brand of monitor is your external monitor for "Tablet Mode"?
Depending on the brand, the method is different
You can try the following, you can try it first to see if it can help you
Press Windows key + K on your PC, select the corresponding tablet in the device list, and follow the interface prompts to connect.
After successful connection, you can choose different display modes on PC:
Select "Duplicate", the tablet will be displayed in the same way as the PC's main screen.
Select "Extended", the tablet will become the extended screen of PC (on the right side by default).
By selecting "Second Screen Only", only the tablet is displayed. When disconnected, swipe up from the bottom of the tablet screen to go back to the home page, go to "Settings" > "More Connections" > "Wireless Display" to turn off the feature. In the wireless display state, you can only use the keyboard and mouse on the PC side to operate, and the tablet only serves as a monitor.
I hope the above information is helpful.
Kirito|Microsoft Community Support Specialist