In the documentation the is a suggestion for a workaround.
After looking at the backed code assets all call PrecachePSOs(); on post load which later calls CollectPSOPrecacheData() with parameters.
I hope they make a tool that gathers objects in a level and potential streams and automates the process in the future.
Do I need to make special PSO caching levels?
While you can capture all needed PSO data from your project’s standard levels, some projects may benefit from creating special PSO capture levels. These levels can be set up so they spawn all assets of a particular type and then capture their PSO data. This is especially true if your project has content that takes time to unlock or is dynamically spawned."
Also this thread might give a clue, it seems there is a shaderpipelinecachetools commandlet