The editor allows you to define “manual folding ranges”.
If the tables in a group are located in the same section of the editor you highlight them and on a Mac press Cmd+k+, (hold Cmd and press k then , while keeping Cmd pressed) and it will fold all the selected text, allowing you to expand and collapse large sections of the editor.
To make it easier to find the groups I add a comment at the top and include that in the folded section so it remains as an anchor to use when expanding and collapsing.
For example:
/*** Table Group ***/
Table table1 {
id integer
}
Table table2 {
id integer
}
Table table3 {
id integer
}