more importantly; rather than that; but
Used to shift the topic or introduce a more important point, often contrasting with what was just said. Can be translated as 'more importantly', 'rather than that', or simply 'but' depending on context.
More importantly, have you prepared for tomorrow's meeting?
Talking about the trip is fine, but let's finish our work first.
Before that, finish your homework first.
Compound of それ (that) and より (than), literally 'than that'. The conjunction use developed from the comparative structure.