When the user adds or edits a template that does not exist ( the page was not created but the title might make sense ) we currently just show the pane to add an undocumented parameter there.
{F34627656}
**Requirements:**
For non-existent templates :
[] Show the following text under the template name using current styling: "This template doesn't ~~yet~~ exist."
[x] Show "add undocumented parameter" input as is, but change the link to red, as the template's page doesn't exist. → Done via T272487.
For subst use case (if `:` is detected in the template name):
[] Show the following text under the template name using current styling: "It is not possible to detect if this template exists or not. Help is not available for adding templates using modifiers, such as [[ https://en.wikipedia.org/wiki/Wikipedia:Substitution | subst ]]."
For unrecognizable wikitext:
[x] Leave current state: when forbidden wikitext characters are used the input is red and the "Add template" button is disabled. Future work could consider adding a warning, but not included in this ticket.