In KMail2 it is not possible to add a filter to the toolbar. (Same as Bug 190827 in KMail 1.) Reproducible: Always Steps to Reproduce: 1. Settings->Configure Filters… 2. Create a new filter named Foobar. In the Advanced tab, make sure that "Additionally add this filter tothe toolbar" is checked. 3. OK 4. Settings->Configure Toolbars… 5. Toolbar->Main Toolbar <kmmainwin> 6. Select "Filter Foobar" from the "Available actions" list 7. Press the right-arrow button to add the filter to the "Current actions" list. 8. Apply Actual Results: 9. The icon for the Foobar filter does not appear in the toolbar. Expected Results: 9. The icon for the Foobar filter should appear in the toolbar.
I don't need to use "Settings->Configure Toolbars…" I just apply and I see it in toolbar. Please verify in 5.x version.
I tested just now with KMail 5.1.3 and can no longer reproduce the problem.