Users are advised to have prior knowledge on how to:
1. Access hidden files and folders in Windows
2. Search files on your computer
3. Edit file contents using a text editor
4. Modify file attributes
5. Understand Unreal Fullscreen parameters

Since this game is using Unreal Engine, the display screen can be modified using Unreal Fullscreen settings.

These are known settings to setup each type of screen modes:

Fullscreenmode=0 <-- Fullscreen
Fullscreenmode=1 <-- Borderless Window
Fullscreenmode=2 <-- Windowed

These are the user settings files required to be edited:
1. GameUserSettings.ini
2. DefaultUserSettings.ini

The steps below describes how to modify the gameusersettings.ini file.

1. Go to c:\users\<your profile name>\appdata\local\deathwatchgame\saved\config\cleansourceconfigs folder

2. Make a backup copy of the filename gameusersettings.ini

3. Edit gameusersettings.ini following the settings below (use the screen resolution as per your video monitor resolution)

Example:
ResolutionX=1366
ResolutionY=768
Fullscreenmode=1
Lastoptionconfirmedfullscreenmode=1

4. Save the file and in the file Properties, set the file attributes to Read-only

5. Go to c:\users\<your profile name>\appdata\local\deathwatchgame\saved\config\windowsnoeditor folder

6. Follow the same steps 2-4 described above to edit gameusersettings.ini

That's it for gameusersettings.ini

These steps below describes how to edit the defaultgameusersettings.ini

1. Go to c:\<your folder path>\steam\steamapps\common\warhammer 40,000 deathwatch - Tyranid invasion\deathwatchgame\config folder

2. Make a backup copy of defaultusersettings.ini

3. Edit defaultgameusersettings.ini following the settings below (use the screen resolution as per your video monitor resolution)

Example:
ResolutionX=1366
ResolutionY=768
Fullscreenmode=1
Lastoptionconfirmedfullscreenmode=1

4. Save the file and in the file Properties, set the file attributes to Read-only

That's it for defaultusersettings.ini

That's all you need to set for Borderless Window mode using Unreal Fullscreen settings.

Reason the files are set to Read only is so that it would not be overwritten when you start the game. To restore your previous ini settings, just copy from your ini backup files (see step 2 above).

Note:
The in-game Settings option is displayed as Windowed Off, just double click the Deathwatch game in your taskbar to display the game in Borderless Window mode.

That's it, have fun!