This is about as basic as a plugin gets. HTML In Widget Titles allow you to use any normal HTML tag(s) in the Title section of any widget. While originally designed for making titles linkable, it should also work for any other HTML tags.
Simply replace the < or > with [ or ] respectively and use the HTML tags like normal.
Instead of inserting: Click This Link
Simply insert: [a href=https://jabelone.com.au]Click This Link[/a]
How it works:
The plugin uses some very basic PHP and a WordPress filter to replace all instances of [ or ] with < or > respectively. This is because when you enter a normal <tag> into the title input area, WordPress will remove it. This replacement happens as the page is generated from the PHP code so it avoids this problem.
If you wish to change what the replacement is than it is quite easy. From the plugins menu select "editor" than in the top right hand corner choose "HTML In Widget Text" and click "Select". Find the lines that look like the ones below and replace the [ and ]. Be sure to not change anything else!
$html_widget_title_tagopen = '['; //Our HTML opening tag replacement
$html_widget_title_tagclose = ']'; //Our HTML closing tag replacement