Is it possible to control the number of plugins displayed in Settings\Plugin Manager? Ihave DPI set to 125% so that may cause the problem but I have two scrollbars and have to slide both to see "Get More.." No problem functionally but visually kinda clunky.
You might be able to utilize Themify to control the height of the containing div. The identifier would be #settings_plugin_pluginmanager_pluginlist. A quick test seems to work in the developer console.