I've just done some experimenting with the new yellow border that appears around selected tables in the query designer.
You can 'lasso' several tables to select them and move them as a group.
This provides another way of (both causing and) fixing the issue raised by the OP.
For example, two tables have been moved above the top of the query window and are now 'stuck'
I've selected all 3 tables below
View attachment 80842
Now select the header row of a table that is visible (tblEthnicityCodes) & drag the table downwards slightly. All three tables move together
View attachment 80843
Problem solved!
NOTE: Click outside the tables to ungroup them again