Just my personal guess: I really doubt GTK has this sort of column "pinning" feature. Probably the only way to achieve this would be to have homebank offer a split view feature where you can assign some columns to one of the two paned widgets, and where the split view / pinning is, in practice, two GtkPaned with independent scrolled views and listview widgets inside of each. But that means, of course, that you end up having two views and two treemodels to manage (and then have to do that for the Accounts dialog and the reports dialog, similar in spirit to bug #1920642)
If you start dividing that with multiple panes, you will also have to remember their width/position, and probably set the gtk_paned_set_wide_handle property to True so that it is visually clear where the distinction is / that they can be dragged... oh and probably the weirdest part would be figuring out some way to keep the two scrolling vertically in sync/tandem.
Just my personal guess: I really doubt GTK has this sort of column "pinning" feature. Probably the only way to achieve this would be to have homebank offer a split view feature where you can assign some columns to one of the two paned widgets, and where the split view / pinning is, in practice, two GtkPaned with independent scrolled views and listview widgets inside of each. But that means, of course, that you end up having two views and two treemodels to manage (and then have to do that for the Accounts dialog and the reports dialog, similar in spirit to bug #1920642)
If you start dividing that with multiple panes, you will also have to remember their width/position, and probably set the gtk_paned_ set_wide_ handle property to True so that it is visually clear where the distinction is / that they can be dragged... oh and probably the weirdest part would be figuring out some way to keep the two scrolling vertically in sync/tandem.