if I am updating my Theme (Arnold) in deleting the old and installing the new then I am loosing all Custom CSS and maybe other changes from the old one. Right?
How can I get all my things transferred to the updated theme?
With “Export current data” and “Import” afterwards?
The custom CSS will not be lost if you remove the theme.
It only removes the files in /themes/arnold folder.
ps: In case of emergency, I recommend that you back up the custom CSS code to a local text file.