To add functions in subfolders, you can use relative paths.
Firstly you will need all subfolders (if you dont want to hardcode them). For that you can use the dir and isdir function.
currentFolderContents = dir(pwd);
currentFolderContents (~[currentFolderContents.isdir]) = ;
Now the currentFolderContents structure contains all subfolders of your current folder as well as the paths to the current and topfolder ('.' and '..' (These should always be the first two entries)).
To add the subfolders to your path use a for loop
for i = 3:length(currentFolderContents)
For nested subfolders use nested for loops.
Hope that helps.