When the data in a cell exceeds the display width of a Treeview column, it gets cut off and the only way to see it is to resize the columns. Is there a way to have a horizontal scrollbar or panning within a column so you can view the data without resizing columns?
Is there a way to implement a horizontal scrollbar within a ttk.Treeview column?
No, there is not.
The official tcl/tk documentation is very comprehensive. If it's not documented, the widget doesn't support it. You can see the canonical documentation for the treeview widget on tcl.tk, where you can see there is no support for scrolling a column.