Is there a way to say QtCreator to rebuild the .ui file from .h?

[wysota]

2.- Is there a way to add a statusbar in QTCreator?

Yes, right click the form and choose "Add status bar". Not that you'll be able to do anything with the status bar from within Designer apart setting its properties...

It can be interesting to say QT People that include this functionality in next versions.
For example, in this way a copy - paste operations could allow to build a menu from code. (for example). But I understand that it can be very difficult.

I don't think there are tools for painters to decompose paintings into blobs of paint and stuff that paint back into tubes.

It's written numerous times in numerous places - never modify files that are generated on the fly (ever, not only in Qt). You are given mechanisms for modifying the looks and behaviour of UIs generated from .ui files in your code so use them. If you stride sideways and go your own way then you will be on your own. Deal with it.