Currently Bootstrap 3 is used in general and Bootstrap3-dialog is used for modals.
Update to Bootstrap 4.
Review and improve responsive behavior (which is far from optimal, at present).
Initially, the app has almost no HTML; the DOM is built under program control - the main structure by the module manager according to the module definitions in the main app edit.html resp view.html.
Currently Bootstrap 3 is used in general and Bootstrap3-dialog is used for modals.