If you've installed another SSD into your PlayStation 5, you can move your games onto that storage device to clean up space on your main SSD. Here's how.

PS5 SSD: How to Move Games to the M.2 SSD If you want to shift over some of the games you've already installed on your PS5, then you can do that with minimal effort.

Note that while the PS5 will recognize an external HDD, know that transfer rates will be impacted, and they are NOT recommended for PS5 games according to Sony’s site. If you can pick up an SSD ...

Those titles need to make use of the system’s internal SSD. For your purposes, it might make more sense to store your PS4 games externally while saving the internal SSD for the games that need it.

Sure, you could just find the game's folder and move it to a second Steam install folder on your HDD, but that'd take like, precious extra seconds.