The procedure to add any package you wish to the Extended Symbolic Math Toolbox is as follows:
1. Find the package of interest. For example, you can find many additional packages at the following website:
2. Extract the files in a directory (for example d:\work\MaplePackage\)
3. Run the following code in MATLAB:
maple('libname := "D:/work/MaplePackage", libname:')
At this point, if you run the code:
you will see a list of functions available in that particular package.