On macOS, Texifier is currently available in two flavours: unsandboxed version served directly from our website, and a sandboxed version available in the Mac App Store.
When you download and purchase Texifier directly from texifier.com, it comes without any restrictions placed on the files it can access. You can open files saved anywhere on your Mac.
Texifier downloaded from Mac App Store abides by the sandboxing rules, which among other things free access to files by the app. Any files that may be accessed (opened or used in the typeset process) must come with explicitly-granted permission by the user.
In its home window, Texifier provides a convenient table entitled “File Accessibility” to allow users to manage access to various files they intend to work on using Texifier. It is recommended that users always grant Texifier permission to the highest possible folder in the hierarchy of documents in order for the file access to be smooth during the writing process.
This is further explained in apps/getting-started/platform-specifics/sandboxing