Even better news - latest Plex Media Server beta = version 1.13.4.5251 has a change that reduces memory usage when dealing with requests as was seen here.
See Release Notice Plex Media Server - #224 by emilybersin
- Shrunk the excessive memory usage when serializing large JSON trees (#8579)
I have tested multi-select with libraries of 13,000+ and 16,000+ music tracks and no crashes. You could try and see if it survives with your library !
