Last answer first, yes, accumulated depreciation or amortization is a negative number as an asset as it represents a total of annual expenses that reduce asset value. The accumulated accounts represent the sum total of ALL depreciation taken for ALL assets and so you cannot just move an account that might be affected by 10 assets underneath just one. It is what it is.

If you wish to have a sub-account for each asset that represents depreciation taken you can do so but you will have to journal entries from the single other asset Accumulated Depreciation to the sub fixed asset Depreciation Taken..It will change the way your balance sheet looks and will show an absolute zero value for any fixed asset that is fully depreciated, causing more confusion than not