I created Indexed columns for this list but i am still getting this error "This view cannot be displayed because it exceeds the list view threshold (5000 items) enforced by the administrator". I created views and When i am trying to display one of the created views in list view web part on a page. How can we display views in SharePoint if we have 20000 items in a list in SharePoint online. Is there any other way to achieve this requirement for SharePoint online ???
We are not supported to increase the list view threshold in SharePoint Online. As a workaround, I recommend you creating filtered views or use folders to manage the items.
Check the article to Manage large lists and libraries in SharePoint
Besides the option to use folders and/or filtered views you should have a hard look at the content in that list. If the list contains more than one content type you could split the list into one list per content type.