I have learned to like this feature when I dived into it. It has been around since the DOS version of Heavybid. This is what Addons by Percent can do in the estimate Treeview. It connects a resource cost like small tools to the total cost of the activity’s labor cost (burdened or unburdened).  The unit cost of this addons resource is the percent of labor to be multiplied by the labor cost. I printed out the Help screen for this feature (see the link below) which details this feature. I would use this for small tools where it varies by activity. The resource code can be part of the resources in the Activity Codebook and can even be a material in the crew set up. This is good for complex projects where small tools applied to the total labor cost is just too broad of a brush. Try it out and see if it fits in your workflow.

HELP

YouTube Video