You can always backup your database in the app settings.
You can do "Reset database" in the app settings - but this will clear everything, incl. the "invoice types" and the stuff in "My company"
What I could consider adding is adding an option to the context menu to the grouping item when you use the "group invoices" feature. For example, when you do "group by year" and then right-click on the "2025" item in the invoices list, I could add an "Delete invoices" button you could use to delete all invoices of 2025. Is that something you'd use?
