Re-adding machines from AD

I have noticed (and been informed by ManageEngine) that if you go to SoM and delete a machine, or if you have the settings set up to delete inactive machines after x days, you cannot re-add from AD, you have to do it manually.

Is there a way to disable this, or do a 1-time sync to import?

We often have temp users who use a machine for a few weeks, they then leave, the machine is collected and placed back in to storage until we get the next temp / contract worker, and it could be weeks before the machine is used again. I want to be able to go to AD Sync settings and re-sync AD to pull all the missing machines back in to Desktop Central.

Hope this made sense.