Shortcut Theming Limitations

Shortcut icons inside pop-ups will always be displayed with their default icon, and their icons cannot be customized. This is for two reasons: First, the shortcuts are controlled by their corresponding apps, and the apps can choose to add or remove shortcuts at any time and, therefore, might reset the icons. Second, shortcuts are often personalized; for example, a messenger app can list your recent chats. Here, icon packs cannot offer individual icons for each chat.
If you add a shortcut to the favorites or app list, you can customize its icon (while keeping the shortcut icon in the pop-up unchanged so that the icons stay consistent). If you use an Anycon pack or Icon Assistant, the shortcut will automatically get the icon of the app it belongs to.