You can download the hi-res image in Legacy(blue) BLOX, it's just a multi-step process...

1. edit the asset.
2. go to the other tab
3. scroll down to the Hi-Res field.
   
4. click/tap View (a new browser window will open) to view the "raw" hi res image.
5. Save the image:
   

It's not just you... tried this on a couple of different sites I have access to, in both clusters(ny,ch) and the UI hangs at the place you mention.

Checking the Dev/Console in the browser I see the error that's locking this up (see below.)

This appears to be a newly introduced bug in the software.

VM303:1 Uncaught TypeError: Cannot read properties of undefined (reading 'answers')
    at S.setData (eval at success (eval at require (tncms.js:5794:6)), :1:5823)
    at constructor.initAsNewAsset (asset.js:4513:16)
    at callback (eval at require (tncms.js:5794:6), :1:12885)
    at ajaxCallback (tncms.js:4210:23)
    at Ext.data.Connection.handleResponse (ext-all.js:40398:6)
    at f (ext-all.js:38225:14)
    at m (ext-all.js:38248:16)
    at ext-all.js:37633:59

https://help.bloxcms.com/knowledge-base/applications/design/blocks/tasks/article_b03d1cf4-484a-11e5-b9d0-4335b25f4abf.html

Everything that's being discussed doesn't address the request of the O)riginal P)oster.

They are asking for the ability to exclude certain BLOX assets from the front end search system... In BLOX. 

They are NOT talking about external search engines (Google,etc) 

The said:

> There must be some way to designate an asset to not be "searchable". Please advise. Thank you!

There isn't... And there should be.