i don't know which one is more crazier

you don't know where taiwan is

or

you know it well but still think it's totally normal and reasonable to do that

Perhaps Xi Jinping and his henchmen should also look at a map? In case they have trouble understanding, here's a hint: Taiwan belongs to that large part of the globe which is "not China".

Just like Panama and Greenland?

Yes. Or sort-of, at least. China is making serious military investments that seem targeted at achieving a capability to invade Taiwan while fending off US efforts to foil such an invasion. In contrast, I've seen no indication that the US is seriously considering taking Panama or Greenland by force except for the bluster from the chief blowhard. Still, that mark of shame will take a long time to wash off.

The nine dash line is objectively and hilariously bad.

If China wants to seize territory internationally recognized as part of other countries... why lie about it so poorly?