Is there a way to Relate multiple records to another table at a time?

I think what you are saying is you have a Parent table and you have say thousands of orphan children, some of which need to be linked to that parent.

It is definitely possible to launch off the Parent record and set what I call a User Focus so the system remembers your launch point. Then you would land on a usual Quickbase report with all the searching and dynamic filters and using grid edit, you could checkbox as many records as you like.

Then when you save the Grid Edit there would be a an embedded report on the parent of those checkboxed but unlinked records. Then you would do one click on the parent to instantly to cause them to be linked to the Parent.

If you were only selecting just a few children like 10 o 20, then a Pipeline could do the linking when the grid edit is saved, but if you literally might select 1,000 children to be links, a Pipeline would be too slow and too intensive on the system for a good user experience.

So yes, it's all possible, but it would probably require us to spin up a consulting Zoom session for an hour or two of consulting time to talk though the spec and get this to work.  If you have a small consulting budget available, please feel free to contact me directly. mark.shnier@gmail.com