Pre/During/Post install/uninstall custom scripts should be placed here.  
A script Template and Mods Functions are included an example to get you started...  

Scripts that are considered:  
**AppID**`-preinstall.ps1`, `-upgrade.ps1`, `-install.ps1`, `-installed.ps1`, `-preuninstall.ps1`, `-uninstall.ps1` or `-uninstalled.ps1`

**AppID**`-override.txt` (the content) will be used as a native **winget --override** parameter when upgrading