No problem.

If you want to install the Real Tracks onto an external, it’s not intuitive and there’s no smart installer. The recent videos help. it’s really easy — just do it manually as I found out.

With upgrades and updates, I run the installer onto my system drive, then copy the files manually onto the external. I then delete them from the System drive to save drive space.

Speaking of drive space, Mojave now lets you move iTunes and movies onto an external without dealing with symbolic links and aliases. As mine is over 300GB, I plan to move it over to the same external where I have RT & Drums. My Komplete, UVI and other sample libraries sit on another external. Although the price of 4TB SSDs has come way down, they’re still more expensive than multiple 2TB drives (and I’ve had those for a few years)..
BIAB 2020 Audiophile iMac Pro 4TB 128GB SSDx2 Catalina; 2012 MBP Catalina
Overture 5 DP 10 LogicProX Finale 26, Encore 5.0.7 SmartScoreX2P Notion 6
Legacy G4-1K DP OS 10.4.11 / OS 9.2 Apps