Log to list format

I am looking for a way to have one file (or other structure) for ongoing logging of activities. What would be handy is a way to have it automagically show up in another file under the associated heading. For example, as I log my activities, tag each line with a client name. In the list format, have all items with that particular client show up. Kind of a daily log to report format sorted by client.

Example:
Log
Item 1 #c1
Item 1 #C2
Item 2 #C1
Item 4 #C5

List
C1
Item 1
Item 2
C2
Item 1
C5
Item4

I have the same need. I think this could be usefull once it done:

The archiver is finished (for now). It could sort of be made to do what you describe, but not entirely.

I think the best solution would be if that grouped list would automatically update, like inline search results. Thatā€™s a point brought up in the transclusion discussion, I think. It doesnā€™t seem that this will be resolved soon (but I may be wrong about that).

Modifying your document through the API to generate those lists is absolutely doable today, provided you feel like hacking together the logic.