If I understand you correctly, you want to create a selection for text. (?)
If you connect a variable to PrintString you can then update this Variable on Input Events.
e.g. 1 is pressed: Set Variable to [Insert text here]
backspace is pressed: Set Variable to [Intro text]
The keys are bound in Project Settings → Input. The Action Events (input) have the name you give them there.
Hope I understood you correctly and hope this helps.