If you have at least two files open
you can create a new EmEditor window
(called here “Group”) in several ways:

– drag&drop one document tab outside
– right click the document tab > “New Group”
– press Alt+Strg+N
– utilize the Window menu

>>I want to have two txt files side by side.
Then best for you would be Window menu “New [Hor|Vert] Group”