I was working on this feature for the custom-wizards plugin and I wanted to fetch all the wizards.
The key used is a string which is unique per wizard. This case was handled by fetching all the rows for the plugin and filtering them based on a for the value which is fine for small number of records but not ideal for a big plugin. It looks like plugin_store_rows is meant to store settings-like data for the plugin.
I personally think, this would open the idea of storing non-settings like data in the plugin_store_rows table.
(Forgive me if it sounds strange)