First you'll have to program a 2nd appearance of the softphone DN, which as far as I know you can't do via a template (but you can do a copy from Mulitline Set Keys and it will change the DN for you).
Then you can do what NEPhoneGuy suggests. As far as putting a call on hold for someone else to pick up, I don't think you can park a call from a softphone but you may be able to do a Call Hold - Remote Retrieve so the other user will have to dial a FAC + the DN that placed the call on hold. So, given that, make sure your extension length setting for the PBX in MiCollab Network Elements covers the length of the FAC and DN's.