Since different editors at national parenting magazines edit different sections, is it okay to pitch different editors at the same magazine, at the same time, with different story ideas for their sections? Or, should I focus on developing a relationship with one editor at each magazine I want to write for (which is what I've been doing with limited success).
It's definitely not only okay to pitch more than one editor at the same magazine, it's recommended. Back when I asked editors for some of their dos and don'ts (see the archive for their answers), several of them said that they get really peeved when a writer hasn't taken the time to seek out the correct editor. So by NOT pitching more than one editor, you're doing yourself a disservice.
Of course, as you note, you shouldn't pitch different editors the same idea. That's just setting yourself up for blackballing. But as mastheads clearly indicated, different editors handle different sections: the health editor isn't going to be interested in your relationship story idea, and the relationship editor isn't going to care about your query on sleep deprivation. So do your research and pitch accordingly. Heck, at Parents Magazine alone, I work with three different editors. All this means to me is that I have three opportunities every month to get a story placed.
Should you focus on one editor exclusively? I dunno. It seems to me that you should focus on breaking into the market, period. If an editor isn't responding to your queries, or you're getting nowhere fast, try someone else. Or consider exploring a different subject which will nab a different editor's attention. No use in beating a dead horse, and just because one editor at a magazine isn't turned on by you, doesn't mean that another editor wouldn't be.
This whole question does raise another point and tangent. And that's using your current relationship to build a new one. And this is always a good thing to try to do. If I have a story that I know editor A wouldn't be interested in, but suspect that it might be a good match for someone else at the magazine, I'll often ask editor A for a referral. If you have a good relationship with him or her, he's always happy to pass you a name (and often drop your name to this new-to-you editor), and you can take it from there. One foot's already in the door.
How many of you guys work for multiple editors at the same magazine?