Right now, pressing the Code button adds a a single tick (`).
It makes more sense for it to add 3 ticks (```) which provides automatic syntax highlighting and can be used for multi-line blocks. Code snippets are more likely to be multi-line than single-line, and even then, the lack of syntax highlighting on the single tick makes it inferior in all aspects except vertical space (as it requires 3 lines at a minimum).
If you’re willing to add more buttons to the toolbar, I’d leave the current Code button with 1 tick, and add a new one called Code Block with 3 ticks. Otherwise, 3 ticks is the superior default.