Short answer: No. Evey does not currently support bulk editing of attendee seat or table assignments. You must update assignments one attendee at a time.
Details
If you need to reassign seats or tables for multiple attendees, for example after a floor plan change or a last-minute event reshuffle, this has to be done manually through each attendee's individual record. There is no Excel-style or spreadsheet interface to edit multiple attendees at once, and no import/export workaround currently available for this task.
Steps to manually update a seat/table assignment
Open the event in your Evey dashboard.
Go to the attendee list.
Select the attendee whose assignment you need to change.
Update their seat or table assignment.
Save the change.
Repeat for each attendee you need to update.