Autoloading the next page would probably require manual fetching and rendering of the search results from their API server so here's a simplified script that just sets the page size.
// ==UserScript==
// @name steamcommunity market page size
// @license MIT License
// @match *://steamcommunity.com/market/search*
// @grant unsafeWindow
// ==/UserScript==
const PAGE_SIZE = 100;
unsafeWindow.g_oSearchData.pagesize = PAGE_SIZE;
unsafeWindow.g_oSearchResults.m_cPageSize = PAGE_SIZE;
unsafeWindow.g_oSearchResults.GoToPage(0, true);
Steam Market Infinite Scroll
I have tried with no success to write a script that auto scroll pages on steam market I'm looking to make it possible to load more listings on one page or all listings. Eg. Show : 10 / 50 / 100 / All (244)