https://whimsical.com/en-1GtxvLCbvPDiBKrwRvkWm
In the CPC hierarchy, directly under the example CPC H01M4/0438 with 3 dot subgroup depth, there are H01M4/044, H01M4/045, H01M4/0459, H01M4/0464, and H01M4/0469 with 4 dot subgroup depth. Each of these has several patent classifications with lower 5 dot subgroup depths.
When you enter H01M4/0438 as a search term for a patent classification code, by the very nature of the patent classification hierarchy, you should get patents with all the patent classifications lower than yours (H01M4/0438), including your own (H01M4/044 through H01M4/0469), and all 14 patent classifications higher than yours (H01M4/0438 + H01M4/044 through H01M4/0469). For reference, the examiners of the Intellectual Property Office assign a given patent the patent classification that is as far as possible at the end node of the patent classification hierarchy, i.e., a patent assigned H01M4/0442 will automatically have the attributes of H01M4/044 and H01M4/0438, which are upper than itself (H01M4/0442) in the hierarchy, due to the nature of the hierarchy.
In this case, due to the nature of a search engine that searches for an entered expression, even if you search using a search extension such as H01M4/0438*, it will not search for H01M4/044, etc. that does not begin with H01M4/0438.
To implement a search that automatically includes lower patent classifications as above, you need to process a mapping data scheme such as "H01M4/0438 vs. H01M4/0438 + H01M4/044 ~ H01M4/0469.
PatentPia Search supports selecting the option 'Automatically include lower patent classifications'. If you select this option,