"Is there a way to re-sort a portal" - yes, you can sort the portal at relationship level, or in the portal definition. You can make those sort criteria dynamic (eg click to see sorted by title, or by author.) But having sorted by title, this bit throws me: "but also move the portal records up so a specific record is at the top of the list"
Do you expect to see something like this?:
I don't know how you will tag the one of the list that you want to see at the top, but it might be easier to fabricate what looks like one portal, but is actually two. Have the first row of the 'portal' actually the direct relatioship to the tagged record, and then tuck below it the 'real', scrolling portal. sorted however you like.
"but also move the portal records up so a specific record is at the top of the list"
By this I mean searching for a portal record, and then re-sorting the portal to bring this record to the top of the portal.
I suppose I can create a new empty field 'Order', then the portal I wish to link to will have a figure such as '1' placed in the field, then the new sort could sort desending by the new field, then ascending alphabetically by 'Title' field.....?
Go for it.