How to make File Open dialog more similar to Finder window? In previous versions of macOS, the File Open dialog had a "Show sidebar" button, "Show items as" and "Group items by" radio buttons in the toolbar. 



In Mojave (not sure in which version this was changed), they're hidden under a hamburger menu:


Is there some way to make the File Open more similar to the Finder window, like in previous macOS versions?
Natively, without the use of third-party software1, no, the Toolbar of a Open File… window is not customizable in macOS Mojave, and its layout was changed from what was the norm in previous versions. It was not customizable in previous versions as well.

That said, you can still use the default Finder keyboard shortcuts to manipulate the window's view instead of using the button menu on the Toolbar.

For Hide Sidebar / Show Sidebar use: ⌥⌘S &nbsp;(Option-Command-S)

Show items as:


as Icons  ⌘1
as List   ⌘2
as Columns ⌘3


Note that other default Finder keyboard shortcuts may apply; however, I only tried the ones already mentioned.



1 Per a comment, there is Default Folder X, $34.95 USD, that may have some functionality that could be useful.

Note that I have no affiliation with its developer nor have I used it. At that price, I probably wouldn't either.