You probably already can do this already via ASM or your own sdat edits, but it is possible to add more songs to the sdat now. You need SymbTool and InfoTool from https://github.com/Gota7/NitroTools. You use "SymbTool.exe symb.bin symb.txt" to extract the symb data and the same for the info data. Then you need to add to the sseq filenames the new filename in symb.txt, and an entry in the sseq list in info.txt. You can also edit what banks hook up to what wave files, what sseqs use which banks, and etc. The fileID is the file id in the extracted sdat. 0 would be the first sseq file in the sseq folder, then it counts up through the rest of the sseq folder, then the seqArcs, then the banks, then the waves. For this reason, you may need to change the fileIDs for all the entries with a greater or equal fileID of than the one you are adding (this goes for seqarcs, banks, and waves too).

Once you are done you compile a new info.bin with "InfoTool.exe info.txt newInfo.bin", and "SymbTool.exe symb.txt symb.bin". You can then use those in your new sdat.

Info.bin should recompile correctly, but I'm more worried about the symb.bin compiling. You won't be able to edit the sdat in DSS due to a current bug in SymbTool.exe. I hope this can help, and you can ask me questions if needed, though I'm usually on kuribo.

Nella carne io sono uno, ma nello spirito, che sono e per sempre saranno sette.