With proton being enabled by default in 89, the page actions menu is gone as this is no longer part of proton to make the user interface compacter as items that are now present in multiple places will no longer be present all these places, so you may have to look elsewhere if the one you are currently using is gone.

In 89, you still can disable proton via the about:config page by setting browser.proton.enabled = false, but doing that you miss on following the new developments and if this is no longer possible in a future Firefox version once proton has been completed.

You can't edit the suggestion you see in the location bar, you can only select what content you like to see.

How can I open a new window when clinking a site in the dropdown from the address bar?

Hmm, I don't see a way to do it with the mouse. In earlier versions of Firefox, you could hold the Shift key when clicking to send the URL to a new window (or hold Ctrl for a new tab). Unlike the old design, holding Shift when clicking seems to be ignored.

Not sure if that is by design or was an oversight. File a bug? https://bugzilla.mozilla.org/

If you are arrowing down to the suggestion, so its URL appears in the address bar, you can hold Shift and press Enter to send the URL to a new window (or hold Alt for a new tab).

Can I edit the sites in the address bar dropdown?

Hmm, in what way? If you mean the default Top Sites list that appears when you click in the bar -- before typing any new text for Firefox to match off of -- that list can be managed on the Firefox Home / new tab page as in Firefox 75-88. See: Customize items on your Firefox New Tab page.