I need to attach more then 10 pages in the site , Is there any alternative way to add more then 10 pages in site
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No, but with Appian 23.3 you can use page groups and drop-down menus.
docs.appian.com/.../Appian_Release_Notes.html
...and to elaborate a bit more here - in 23.3 a Site can have up to 10 page groups (each of which acts as a drop-down menu) and each page group can have up to 10 pages - so that's a total of 100 pages per Site.