I have searched and searched but cannot find a definitive answer. Is there no way to import characters from 2 to 3, like from 1 to 2?

No. They didn't make that available for MM3. Actually there are only two pairs of games in the Might and Magic series that allow character import: MM1 to MM2, and MM4 to MM5. The rest you start with new parties each time.

Basically no. MM3 uses a completely new engine.

If you could import the characters as they were, they would be waaaay overpowered for starting MM3.

The closest you can do is create them with same race/class/alignment/sex and then use an editor to modify their stats. My advice though, is to keep their starting stats normal. It would be too unbalancing to increase them too much.

And one more thing, there are 2 new classes: druid and ranger. It's really useful to have at least one of them for the walk on water spell (you can use a hireling too).

To be fair, importing characters as they were from MM1 into MM2 would also result in a party that was much too powerful, which is why importing them de-leveled them and didn't bring any of their equipment along. Something similar could have been done for MM3, but I think the designers decided not to since they had an entirely new combat system.

True. Come to think of it, even with the entirely new combat system, there is no reason not to be able to import name, stats (with a lower level even dropping them to level 1 would be ok), sex, race and class. That's all that was imported for MM2 from MM1 anyway. Only portraits would have to be chosen or randomly assigned. The new combat system would not be affected in any way...

Only issues I see:
_Extra spells would be lost. You only get the spells your class normally starts with in MM3.
This would have no effect for level 1 characters, but unlike MM1 and MM2, MM3 only gives new spells for new characters, you gain nothing when gaining levels.
_MM3 only allows 2 characters of a given race per sex. 6 dwarf party would not work...