Similar as dark mode toolbar bitmap, user can create 4 app button icon files when make App, they are used in different situations as follows.
AppIcon_name.png: origin light mode, essential
<AppIcon_name>_dk.png: origin dark mode, file format should be same as light mode AppIcon file.
<AppIcon_name>_dk_hi.bmp: origin dark mode with High DPI
<AppIcon_name>_hi.bmp: origin light mode with High DPI
note: High DPI means Resolution>1920X1080 and dpi>=150
App Toolbar Icon are similar(note: App tool bar icon is specified in Toolbar Icon editbox under App branch in package manager dialog).