I just came across this problem with segments. I need to create a segment within a rather small list. While I could create all kinds of rules to try and match the subscribers, I basically just want to select those subscribers I want to be part of the segment. It doesn't need to update automatically, I just want to be able to mail a particular group of subscribers.
Is this feature lacking, or am I looking in the wrong place?
It's not possible to just manually select subscribers and add them to a segment. What you could do though is export your subscriber list and add in a new column/field and add in something like yes/no to denote if they should be flagged for that segment or not and reimport (that will update the subscribers with your new field). You can then create a segment based on that field and capture just the yeses (or whatever you choose to add).
Of course, but as I'm limited to 10 custom fields only, I've got to be careful to create a custom field for any segment I need. Moreover, I takes a whole lot more time to do this export-create custom field-import thing, compared to just selecting those subscribers you want to include, right?
True. You could just create a new list. Segments are generally meant for something that would continually update, not just a 1 off list for 1 time use basically. If it's a fixed list of certain subscribers a new list might actually make more sense.