Hi Jaydeep,
For the mentioned use case follow the below steps:
Steps to follow
1) Introduce an input control mapped with a local variable called TextVar of Text data type
2) Define a local List variable of Text data type
3) On the button click append the current Input Text Variable value (i.e. TextVar) to the local List variable as shown below

See this sample app | TextDemo
Hope this helps you!
Kind regards,
Benjith Sam