At first: You can use "search in files" in Swat 4\Content\System folder, 3rd tab of Ctrl+F in the notepad++

Array

1. Open file: Swat 4\Content\System\SwatGUIState.ini
2. Search for ScreenResolutionChoices keys
3. Replace all (4 - I guess) lines with the following lines:

ScreenResolutionChoices=800x600 ScreenResolutionChoices=1024x576 ScreenResolutionChoices=1024x768 ScreenResolutionChoices=1280x720 ScreenResolutionChoices=1280x1024 ScreenResolutionChoices=1366x768 ScreenResolutionChoices=1600x1200 ScreenResolutionChoices=1920x1080 ScreenResolutionChoices=2560x1440 ScreenResolutionChoices=3840x2160

Translation

4. Open file: Swat 4\Content\System\SwatGame.int with notepad
5. Search for same key - "ScreenResolutionChoices" (for me it's on line 11)
6. Replace this line with: ScreenResolutionChoices=("800x600","1024x576","1024x768","1280x720","1280x1024","1366x768","1600x1200","1920x1080","2560x1440","3840x2160")

Q: Step 4 - I don't have SwatGame.INT file Q2: Screen resolutions are still 4 A: Probably, you have a game with a different translation, i.e. for example, for the Russian version of the game, the file will have a different file extension: SwatGame.RUS. Try to find yours

Q: How it works? A: You specify an array of screen resolutions - step 3, then in step 6: you fixing a translation to add new screen resolutions to settings

Q: I have another resolution, 2000x100 - for example A: You are free to change "ScreenResolutionChoices=1024x576" to "ScreenResolutionChoices=2000x100". After it, you need to change translation file too - step 6

Taken from: https://www.pcgamingwiki.com/wiki/SWAT_4#Widescreen_resolution