How can I search for safari extensions?

I have the same problem as Ian, and in the same timeframe. I am using the most recent build (18G95) of OS X Mojave 10.14.6 which includes App Store version 3.0, build 1003.3. App Store search worked for me with the initial release of Mojave in July 2019.  It ceased working after one of the two, subsequent upgrades.

As Ian noted, the App Store page that comes up for Safari indeed does not have a search option. Nor does Command-F does open a search window. (Command-F does make a quiet, comforting "beep.")

This the missinq search function creates creates a problem for users of 32 bit browser extensions. Apparently, 32 bit programs became obsolete with one of the two security upgrades to Mojave.

I upgraded to the latest version of Mojave on 9/21/2019. On 9/22/2019, my versions of the Evernote Web Clipper extension ceased working in Chrome, Safari, and Firefox. It still worked in Opera. Apple has provided pop-up warnings about for 32 bit Apps and Extensions for some time. Apparently, now's the time.

Here are workarounds for Web Clipper that in principle might work for other extensions:

Chrome -- I was able to fix Chrome by navigating to Chrome Preferences/Extensions, then deleting Web Clipper and re-installing through Chrome directly, not through App Store.  This suggests a 64 hit vershion of Web Clipper is available. 

Firefox -- Navigating Firefox/Preferences/Extensions & Themes opens the window "Manage Your Extensions." I deleted Web Clipper, then used the conveniently located "Find more extensions" box to search for and re-install Web Clipper. The Web Clipper icon didn't show up on the menu bar as it had previously, but I was able to restore it by tapping '»' on the menu bar and using "Customize Toolbar".

Safari was hopeless:

• Navigating Safari/Safari Extensions brings up the defective, search-free App Store home page.
• Apple claims that Safari auto-updates Extensions. It does not do this tor 32 bit extensions, apparently.
• The App Store home page is supposed to let you fetch updates manually.  It says, "Select Updates in the lower-left corner of the window. It appears only when updates are available."  No updates were shown on "my" home page, where they used to show up.
• Navigating Safari/Preferences/Extensions brings up a page showing active and disabled extensions. All of the 32 bit extensions had been removed, which is probably which they could not be updated automatically.

I have an old Logitech trackball. Oh dear, the current Control Panel is 32 bit. I am going to take a nap before dealing with this. ☺️

Hallo MacJack! This has apparently changed in Safari 12.1.2. Like the OP thearenav when I go to safari > preferences > extensions > more extensions (or use the Safari menu) I also get taken to the App Store, and there is no search facility, which is annoying. The old extensions Gallery seems to have disappeared. It now looks like this: (sorry about the German!)

Hi Eric! Yes, I'm running the latest OS, Mojave 10.14.6 (Safari 12.1.2, App Store.app 3.0), After doing a quick google I found this article explaining that the Safari Extensions Gallery is no longer available as of now, September. So we are stuck for various reasons with the App Store. No big deal for me personally, as I've only ever used one extension...Ka-Block!

https://lapcatsoftware.com/articles/Safari-extensions-gallery2.html

Well, I find Ka-Block! is very good everywhere except, as you say, with YouTube! It used to work with YT, but they seem to find ever cuter ways of neutralising adblockers! I’m staying with Ka-Block! for now...never had any conflicts with it, and as far as I can see it doesn’t slow Safari down. But thanks, I‘ll give uBlock Origin a whirl tomorrow when I have time, as YouTube ads are irritating me more and more! Best, Ian.

The search option should be in the upper right of the window?

Hi Ian, but I am running Safari 12.1.2?

Your App Store is High Sierra or earlier and his is Mojave?

Could be...

Thanks! From what I gather it looks like the world of Safari extensions/adblockers is going to change somewhat with macOS Catalina!? We‘ll soon see...🧐