Hi sipon,
there is a way for you to edit the css file and don’t get the unsigned message. Before I say how you do that you have to know that at this point my support ends and you can break the hole thing.
You can enable the „debug flag“ to load unsigned extensions. Take a look here. Scroll to the paragraph with the title „Debugging Unsigned Extensions“. Here you can read how to set the debug flag. Remember this is originally only designed for developers and not to end users.
HKEY_CURRENT_USER/Software/Adobe/CSXS.8 is for CC 2018, HKEY_CURRENT_USER/Software/Adobe/CSXS.7 for CC 2017 and so on.
Again I don’t recommend to do this unless you are sure what you are doing. I’m planning for the next version to give the user more possibilities to manage the size of the buttons.
Thomas