Custom Relief Society Committee Callings

Our Relief Society has a number of committees in addition to the standard compassionate service committee (Activities committee, service committee etc). For compassionate service committee members, we assign sisters to the standard calling (Relief Society Compassionate Service Coordinator, or Assistant Coordinator). However for all other committees we have to assign them custom callings, which we're encouraged to avoid.

Is there a way to add additional committees or 'classes' rather than just having a jumble of custom callings under the generic relief society subheading?

There isn't a way to do this that I'm aware of, unfortunately.
Out of curiosity, what's the difference between compassionate service and service?

Ok great to know. That's a great question and one I've asked the RS president myself. In our ward, compassionate service provides meals for sick, elderly sisters and new mothers (which we have a lot of). Compassionate service finds other service opportunities for the sisters to do and coordinates service-oriented activities. We have a lot of young families in our ward, so I think it spreads our the CS responsibilities a little more.

I'd avoid a custom calling when there is a standard calling available. The biggest reasons is that custom positions has no special access to on-line tools - regardless of what they are called. Standard positions may have some rights attached to them, depending on the calling.

But in the case of the committee, there are no rights.

The Relief Society Activities Committee sounds like it should be using the standard callings for Relief Society Meeting Coordinator and Relief Society Meeting Committee Member.