Hello.
Yes, you can.
In the menu “Sitemap” there are a few submenus. Each submenu (except for “basic settings”, “order of elements”, “restore settings” and “about”) is for controlling each WordPress data type. For example, options in submenu “authors list options” controls which authors will be display and how.
When you click on such submenu you will see options for this data type. In each of these submenu there is an option “display SOMETHING”, where “SOMETHING” is the name of this data type. For example, when you click on submenu “authors list options”, there will be an option “display authors” in displayed settings. Checking this field will display this data type in sitemap, unchecking it – remove it from the sitemap. Remember, that after any change in option you should click on the button “save options” or similar which is on bottom of the list of settings.
In your case you should select one by one each option which control any data type – except custom posts type – and unchecked “display SOMETHING” setting in each of it. Then you should click on the submenu “custom post types options” and make sure that option “display custom post types” is checked. Then, you should click on the tab “custom post types list” and there you can select multiple custom post types to be displayed in sitemap. To do this, click on the dropdown field and select one custom post type from the list. If you have done this step in the dropdown list which was empty, there will be added another empty dropdown list where you can select another custom post type from the list. If you want to change the order of the custom post types, you can click on one of the arrows next to the entry to move it up or down. Clicking on the “X” button deletes the entry.
You can also look on help which is one every settings page in each submenu for “sitemap” menu. Help in WordPress is available when you click on the “help” button located in top right corner of the administration panel. There are information for each option and each setting. My answer above was partially copied from this help.
