This article contains more information the error 'The search query has exceeded the maximum depth of nested search queries'
You can nest a search query within another search query, but this only works on one level. It is not possible to nest a nested search query within another search query, as this would create two levels.
If a search query is already nested within another search query, you cannot nest an additional search query within it. You can check this by clicking on the trash icon next to the search query in the Search Queries section.
Unfortunately, it is not allowed to nest another search query within a nested search query; this is limited to one level. It is not possible to nest a search query at level 2 within a nested search query.