The "custom template" for unknown tags is really useful but extremely well hidden and rather quirky to use

1) The shortcut in the context menu just says "Template" ...no indication of what it does.
I suggest we call it something like "Setup template for <the tag name>..." ; that describes what it does plus has ... to show a dialog will come up

2) The actual dialog allow me to type in any text for the tag, I instantly tried <button> but that is wrong it should be just button. Help the user here
I also tried putting rich:calendar but it does not look like it supports template translation, only simple basic tags - then we should just have editable combo list with choices here.

3) Give a preview of how the tag will look like in the dialog

4) The Template editor in preferences has no instructions and no Add button; at least explain the the tables contain existing prefreences for already configured templates and tell them about the "Setup template.." action in the context menu.

....It also contains 2 lines with some names I never setup (i.e. unknowntag-1, unknwontag-2) - remove them.