Can I ENABLE the "enable editing" protection on one file after I greenlit it?

Every place I've looked, people only want to *disable* the protection as it's a nuisance and it some circumstances it merely slows them down. However I'm trying to "turn on" protection for an individual file. (I already have the Trust Center settings clicked.)

Here's a sequence I did. Windows 10, Excel 365 (jeez Louise, I THINK that means 2016)
1. Saved foo.xlsx from an email to a C: folder
2. Opened foo.xlsx
3. Got the yellow banner Protection warning "~~files from the Internet are not safe"
4. Closed the file. (BTW it did what I wanted or expected.)
5. Outside of Excel, copied foo.xlsx to test.xlsx
6. Opened test.xlsx
7. Got the yellow banner "Protected view - be careful..." and the button to enable
8. I clicked to Enable editing.

Now apparently this unflags the file properties. In explorer file properties, it does not show the blurb at the bottom "this file came from another computer...", nor now does it have the checkbox to unblock the file in the properties dialog. I'll regard that as a nice convenience, that it "remembers."

First, verify or assert that the above happens to you, and that I'm not in a misbehaving condition; I say that because it "seems" to permanently unflag some "protected" or "unsafe" file property when you click "Enable editing". (If on your box, if it asks again the next time you open it, maybe I have a configuration issue)

But here's an apparently nasty side effect. If I delete test.xlsx, and do steps 5 and 6 again, no banner warning now, and no blurb on the file properties! It's as though Excel didn't just unflag the file itself, but set up some kind of "trust" for any file named test.xlsx. You see, foo is still "dirty" so to speak, and I want Protected View to occur when I open any copy of foo. It DID do that the first time, but after I Enabled Editing, now, even a freshly created test.xlsx doesn't get the banner.

The danger is that when I copy some other downloaded file to delme.xlsx, will it get the banner, or is that a "trusted" filename now?

I know that .xlsx suggests no macros so this might be regarded as overkill paranoia, but the truth is that I actually want the banner prompt in this circumstance.

So: is there a way to "untrust" delme.xlsx?

Bonus question: is there a way to "reflag" a file? You know, when you right click the folder entry and view properties, once you tick the checkbox to unblock a file, you aren't given an opportunity to reverse your choice.