I've recently found ShellExecuteA and W.
1. Why are these not in any of the documentation categories except Forum? i.e. why are these undocumented in the mql4 codebase, yet the function exists?
2. What are the return codes from this function?
3. Where is decent documentation?
4. How many other ShellExecute functions exist?
1. These are not MQL4 functions and therefore do not belong in the MQL4 documentation. The ShellExecuteA (Ascii) and ShellExecuteW (Widechar) are Windows functions and ...
2. ... their return values can be obtained by reading the appropriate Windows API ...
3. ... which you can find here: Windows Dev Center
4. ... look at the link above
To give a more indepth answer. It is possible to call Windows API (functions from Windows dll libraries for example) within MQL4.