As per my understanding you want to encrypt .mlapp app designer file without using MATLAB Compiler.I don’t think you can encrypt source file of a MATLAB app designed in App Designer without MATLAB Compiler because Designer Files are MATLAB Code files which can be easily read and modified by anyone access to file.
If you want to protect source code of your app designer app, you can use MATLAB Compiler to create standalone executable or shared library. This will compile your code into a format that can be run on any machine without requiring MATLAB Installation. This compiled code can also be encrypted to protect the source code.
