The following seemed to improve the performance of Abortext Editor, although not completely.
renamed the arbortext.wcf file in
C:\Users\username\AppData\Roaming\PTC\Arbortext\Editor
to have the ext .old.
Closed AE and reopened so that the .wcf would be recreated.
We were having a lag time of about 30 seconds when trying to access the "modify attributes" . This is was much quicker now. The loading of an xml file did not improve, it is still slow.