I want to load multiple symbol libraries at once

Where do you want to load them?

Eeschema normally loads all schematic symbols from all included libraries at he moment you add the first schematic symbol to the schematic.

A screenshot of where you want the libraries may help your explanation.

KiCad does not search for libraries, and only uses libraries specified in the sym-lib-table files. More about library management in:

Or read the documentation on:
https://docs.kicad.org/

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