i have about 100 fields now and it is impossible to find things quickly because i don't know how to logically arrange them in the Field Explorer bar...
any help?
I add them to groups. If you add them to groups first, then you dont have to change your form. If you add them after they are in groups, you will need to rebind.
Unfortunately it's the nature of the beast. Groups are a good idea. I found that if you're using InfoPath 2013, if you move fields around, then they should rebind themselves. Not sure in 2010, I'm guessing that's not the case. Also in SP2013, when you click a field on the form, it auto-highlights the associated field in the data manager. I don't recall this with SP2010.
So, the short of it is you're stuck with it, but if you upgrade to 2013, you should be looking better ;)