After updating to 0.8.14, I found that the checkboxes have been modified, added a strikethrough and looked more muted. However, I use checkboxes for answers of questions rather than to-do lists. It seems weird to strikethrough the right answer, for example
Hi jack, the method described above has changed. It’s recommended now to put your custom CSS files into .obsidian/snippets and then activate them in the Settings->Appearance page.
Open your favorite text editor (for example, “Notepad” if you’re using Microsoft Windows), and paste the text into the editor. Then click File → Save As, and save it into the vault/.obsidian/snippets directory as a file ending with “.css”, for example “checkboxes.css”.
Because there’ no class or id that marks this as a completed task in edit mode, it looks to me like there’s nothing to target with CSS, so there’s no way to style it.