Views is basically a wrapper for the native WP_Query, which queries the database to retrieve posts according to the arguments you supply.
When you set a Query Filter in a view that is 'permanent', it is effective every page load.
When you add a custom search filter, that works by adding a url parameter and refreshing the page. The presence of that url parameter prompts the view to add that filter as a search argument.
If you use the same 'thing' (e.g. taxonomy, custom field) for the Query Filter and the custom search filter then once the page is refreshed with a url parameter present it is trying to apply both, possibly conflicting, rules for the same thing.
Let's say the results may be unpredictable and doing this is unsupported.
If you create a new View and specify that it is a custom search then the UI for adding a 'permanent' Query Filter directly is hidden, you can only add the parametric filters using the New Filter button in the Filter Editor, unless you change the screen options at the top to expose the Query Filter section (or if, when creating the View, you choose to set up options manually).
You would expose the Query Filter section if you wanted to add a permanent filter for one 'thing' (taxonomy, custom field etc., perhaps 'author' in your case) while having parametric filters for other things.
It sounds like you want to pre-select some of the search terms your users might select, so if there are taxonomy terms 'books', 'videos', 'plays', 'magazines', & 'web articles' and you want the page to load with the first three of those pre-selected, then bear in mind that with a custom search these are set by the url parameters.
So, if you add this view using just custom search filters to a page and visit it. Now select the terms you want to pre-select. The page will update the url to include the search terms with a parameter 'wpv-category-slug'. There will also be additional parameters that you can remove. If you copy that url then you can use it wherever you link to this page so that those terms are pre-selected when the user first visits it.
I hope that helps you achieve what you are looking for.