Hi,
Well, that option is not exactly for that purpose – it is for “Select all” checkboxes, which is not the same as search everything. For this to work, you need to add all the other post types as well to the filter.
However, I think there might be a way to “hack” this with some custom CSS, but I am not sure if it will work:
1. First, choose all the post types you want to search, under the filter options: https://i.imgur.com/NHzuGx6.png
This should print additional checkboxes below the existing ones, they should be unchecked: https://i.imgur.com/y3WQBjR.png
2. Apply this code to your theme custom CSS field (if it supports it) or use the custom CSS field on the search plugin back-end:
fieldset.asp_filter_cpt .asp_simplebar-content>div:nth-child(n+5) {
display: none !important;
}This custom CSS will actually hide the newly added checkboxes – but they will still act as a filter. When the user hits the “Search all” checkbox, these filters get “checked” invisibly, enabling the search on all of the selected post types.
We can only hope this works.