If they are different assets, in many cases that treatment is not allowable.  They need to be reported separately because gains, losses, and depreciation recapture all need to be factored in for each separate asset because they may be treated differently.  Just netting them all will often have a different and wrong result

If it was all part of one asset (such as a house with additional improvements), you are right, some software allows you to 'group' them like that to report it as one item.  Unfortunately, ProSeries is NOT able to do that (it seems like they set it up to do that, but it doesn't work).  But as I mentioned before, if you have separate assets you are not allowed to combine them anyways.