Personal material labrary

I’m trying to add my own materials to the v-ray preset labrary. I have successfully added materials into my own folders through the root directory.

Problem:
I would like to add folders inside foldes, but it only seems to register 1 layer of folders. Is there anyway to mitigate/change this?

Ideally I would like a folder named ''wood" and inside that folder have multiple folders like “oak” “walnut” “beechwood” an in those folders I would place my many different oak materials.

I like the workflow of having the preset library inside v-ray, hope you can help me in with this.
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In V-Ray 3.6 the library functionality is limited to the default preset materials. There is no workaround for listing custom folder trees.
All this is fully covered in the upcoming major update based on feedback precisely as yours. Let us know what other workflow improvements you would like to see in V-Ray for Rhino.