Struggling with the same issue.
Anyone know of a way to ‘unlock’ a theme once a site has been built?
I am relatively inexperienced, have built my site, and am now polishing off some speed optimizations. I have been struggling to eliminate some render blocking css - bootstrap.min.css and a few others that I believe are part of the introductory theme I chose when I started.
I have concatenated and ‘cleansed’ my various css files (including bootstrap.min.css) and was hoping to use the merged css file as a new theme to replace the default bootstrap.min.css file (as per suggestions like this).
But I have hit a dead end.
Any help would be greatly appreciated.