How do I view only specific extension types in Outlook's "attach file" explorer window?

I send a lot of, nearly exclusively, .docx, pdf, or .xlsx. Whenever opening an explorer window following an "attach file" command I'd love to be able to only see the files with these extensions within this window.

I know how to group files in a normal Explorer window, but it does not seem to work in this case.

How do I view only specific extension types in Outlook's "attach file" explorer window?(Please, no suggestions of changing my workflow.)

In the explorer's search window,

you can enter multiple wildcard criteria to filter what you want. Using the following will only display PDF, Word and Excel files;

*.pdf OR *.xlsx OR *.docx

In the Places Bar on the left, you can right click on Favorites and choose Add current location to Favorites. This will give you the ability to have a single click filter.