There's wicd, but it seems as if it's not maintained anymore. However, I've had the problems you described with wicd on another slackware distro, so maybe it's a slackware problem somehow?
After installing AbsoluteLinux 14.12 I had some trouble with networkmanager. I downgraded to version 1.0.6 and that works fine for me on a Lenovo u330p. Connection sometimes drops when connected to the WLAN at work, but that's probably due to insufficient coverage. At home I've had no problems at all.
I could send you the 1.0.6 txz package should you want to try it (if you can't find it in a repo somewhere). Drop me an e-mail (my address is in the user list)