Cannot place icon on toolbar (9.0.0 + Thunderbird 115)
Allow HTML Temp 9.0.0 Thunderbird 115.2.0 RC1 64bit Windows 10 Pro 22H2 64bit
The icon is located only on the unified toolbar. They cannot be placed on other toolbars by customization. I would like to see this problem fixed.
On the other hand, in Thunderbird 117.0B5 64bit, I can place icon in the toolbar customization. However, it did not work properly.