Hi Marek, I've attached a plugin that should help.

It puts up a dialog box with a list of styles in it and this styles list can do multi select, it will delete the ones you select.

There are instructions for how to install a plug-in here:
https://moi3d.com/faq#Q:_How_do_I_install_a_plug-in_script.3F

Hope that helps!

- Michael