Using your working copy of the sound file, click on the "SOUND" icon in the file organizer panel on the left side of the window.
This will open the sound project sound slot templates overview page.
The Sound Project Overview page is divided into four quadrants.
Upper Left - Sound Project Sound Slots
Upper Right - ESU Sound Library File Explorer of ready-to-use Sound Templates
Lower Left - Windows File Explorer that works just like the desktop app to copy and paste data from your own files
Lower Right - .wav file table - this is a list of every .wav file currently copied into the sound project.
Every .wav file in this table gets written to the decoder when the file is uploaded whether it is used in a template or not. The .wav file table also shows the size of the individual .wav files.
Also note that the decoder type, and current memory status is displayed at the bottom of window.
The LokSound 5 decoders have a good bit of memory to work with. I was able to edit this project without any issues. You may have to delete some of the .wav files in the project or even trim your own custom .wav file depending on what you are trying to do.