Hi,
You can not add the account code to the Labor tab today. In addition all allocations of labor costs are done via the labor allocation rules. Thus, what you can do is build a rule that assigns a fixed value or a percent of base to a CapEx account. The caveat here is that if the amount changes over time or if you can not set a standard using the granularity of the labor allocation rules this option will not work.
The other way to do this if the above is not feasible is to do your capitalized labor in the other tab so you can change the numbers as you see fit. Then when you group/filter by labor on the summary tab you will see the total you are looking for.
Please let me know if you need any clarification,
Lauren Griessel