Under metric templates, when you want to enable a metric, you select the checkbox. Then you look at the bottom of the page. There's a disable collection button but no "enable". just a blue "play" arrow. It should be more consistent. A play arrow doesn't really make sense there.
this is a cosmetic issue, but also one that wouldn't take more than an hour to fix and make clearer. i'm going to target for the 1.1 time frame, to see if it gets picked off as low-hanging fruit by anyone.
Those play arrows are in several places. I've always hated them. Since it doesn't seem we'll get usability help any time soon let's just fix them one by one. Replace the play button with an Enable button.
This should be a "set and enable" button. A simple "enable" where the user only has to choose the metrics, without giving an interval is plain missing.
next release
This bug was previously known as http://jira.rhq-project.org/browse/RHQ-339
Moving this to ON_QA -- test it, and if it is not fixed, move it back to an assigned state.
Still an issue in RHQ master branch. This UI page hasn't been GWT-ized yet.