how to show more than 500 characters of helptooltip for a dropdown?

Does the OOTB tooltip attribute of components not work for you? It's not clear in your post if you had tried that already, but it should support just about 500 characters per my testing. If you need more characters, then I would consider instruction text or a rich text component. For large amounts of help information, I would think it might be easier for a user to read if on-screen instead of a pop-up.

           a!textField(

             label: "Test Field",

             labelPosition: "ABOVE",

             helptooltip: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla bibendum diam odio, in viverra urna ultricies eu. In vel nisi mi. Proin pulvinar, tellus in sollicitudin luctus, nulla purus placerat ante, in tempor neque turpis ac orci. Suspendisse eleifend, lorem et tempus mattis, dui leo semper ipsum, vel consectetur lorem elit a nibh. Cras cursus enim ut laoreet ultrices. Morbi consequat feugiat laoreet. Sed tempus, urna at pretium sagittis, quam sapien blandit enim, quis laoreet erat nisl sed.",

             saveInto: {},

             refreshAfter: "UNFOCUS",

             validations: {}

           )

If your help tooltip is going to be that long maybe you should try to have it in a separate section at the bottom of your interface, display it in a read only text field and just add in your tooltip some text like "Please refer to Help section for more information". If you need to have all the information in the tooltip you can establish some logic to display a specific text for each option on your dropdown so it will only display the information needed.

Anusha,

Based on my understanding of your question, there is not OOTB way of achieving what you're looking for (have hover over descriptions for each distinct value in a dropdown). There are workarounds you could do to achieve this:
1. Once the user selects a value in the dropdown, display a side-by-side field with the specific description. This wouldn't give them the ability to view the description real-time when selecting, but would be better than nothing.
2. You could restructure the design to be a two column selectable grid where the name and description would both display when the user is deciding selection.

Best,
Ashvin

Yes tried this already. Howevert, used rich text field with a clickable link to show the description when user wants to. Thanks