Closing all sublayers of all layers at once?

I have a Rhino 8 file with 30 layers each with 4 to 20 sublayers. I usually work with a layer menu that does not have the sublayers on display, i.e. > arrow.
If I forget which layer a sublayer is part of I use the built in search function all of which is fine.
When I want to return to the full layer listing I delete the current layer search keyword and on return all sublayers of all layers are in their ‘dropdown’ state.
How do I get all sublayers to return from their dropdown state ? Do I have to go thru each of 30 layers manually and click on dropdown arrow ‘v’ to return to the ‘>’ arrow ?

H @Charles_Cary,

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– Dale