Please explain in detail what do you want.
It is possible to split the workspace area to get files displayed side by side (vertical workspace split) or above / below (horizontal workspace split) as Frank have already written, see power tip Vertical & Horizontal Split Window
It is possible to split the document window of a file horizontally to work in same file on two different positions or always see the header row on viewing/editing a CSV or fixed width file.
It is possible to split the document window of a file vertically to see left always the beginning of the lines and horizontally scroll only right side of the lines which is useful on viewing/editing a text file with very long lines, see power tip Vertically split the edit window
It is possible to get two files displayed side by side with a synchronized vertical scrolling of both files.
It is possible to duplicate a document window 1 or more times to have 2 or more instances of same file opened in same instance of UEStudio, see for example power tip HTML preview
And it is of course possible to use multiple instances of UEStudio.
Please provide also information about:
- version of used UEStudio as shown in Help - About,
- used GUI mode - ribbon mode (default since v16.00), or toolbar/menu mode with contemporary menus (alternate mode since v16.00, or toolbar/menu mode with traditional menus (second alternate mode since v16.20 and mode used prior v16.00),
- used file tabs / document window mode - dockable or not dockable file tabs - as shown when right clicking on a file tab and looking on first menu item in submenu File Tabs in opened file tab context menu.