Hi! The case solution pages have not <yet> been ported to client side human service versions like to the other case/task related pages. This means they are still the class case widget style as you know and creating custom widgets for those is a bit more complicated.
The good news is that for that exact reason and your exact use case, we created the Markup widget that allows you add your own HTML widget to the page.
Here is a blast from the past that shows you how - https://www.ibm.com/support/pages/node/1280752
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