Custom Properties not editable in imported model

I imported a step file of a part from a vendor.  It imported fine, but I can not edit the custom properties at all.  I can not delete the existing custom properties and I can't add new ones.  ll the lines in the custom properties box are greyed out.  I have never seen this with other imported files before.  I am running SW 2018 SP2

On a regular part the first 3 columns are not greyed out

SolidworksImport export