Tags in Windows 10 - a few questions

[ABB125]

I recently bought a new laptop, and yesterday transferred my picture and video collection onto it. All well and good.
My collection is split into two part - railway and non-railway. My ambition is to have every item in my railway collection tagged with stuff like location, unit number, operator etc, so that I can (for example) search for "CrossCountry class 170 BHM" and see every picture I have of a CrossCountry class 170 at Birmingham New Street. I've slowly been tagging stuff over the last two years, and am most of the way there.
However, today I tried to tag some recent images and videos on my new laptop, and came across a few issues:

• There was no "autofill" drop-down suggestion box (of all previously-used tags) as I typed in tags as I had previously (eg: I type "cro" and "CrossCountry (Arriva)" appears on the list).
• In order to search, I now have to prefix my search term with "tags:" in the search box (eg: tags:bhm), when previously this wasn't necessary (ie: I could simply type in "bhm" and see everything at Birmingham New Street).

Courtesy of https://answers.microsoft.com/en-us...complete/65e6fee9-e98f-443c-8ca0-969f4988c6d0 I have now got a drop-down list appearing. However, the only tags appearing on it appear to be ones embedded in PDF documents that I can't get rid of. None of the tags that I actually want to appear (such as "Diesel Locomotive" or "Freight") come up on the list. This is irritating for three reasons:

1. I don't want to have to type out long tags every time I use them
2. I'm liable to make occasional typos, which are likely to mess up the system
3. If I wanted to see which members of a particular class of train I have pictures of, I could type 220 into the tags box, and a drop-down list of all class 220s pictured would appear. No longer!

So far these are the main changes I've come across, although there may be more I haven't found yet.
Is anyone able to provide any assistance? Thanks very much if you can.

EDIT: I've found another issue - some of my pictures I run through some HDR software, and the output file has "HDR" in the filename. Previously I could simply type "hdr" into the search box and all HDR'd images would appear. This no longer works.
EDIT 2: I think the issue is that "hdr" is only three characters and thus the search no longer works. Typing "medium" does come up with results as expected.
Another question I've thought of is why do I now have to press enter to search? Previously the search would start as soon as I started typing. (This isn't an issue per se, mainly curiosity.)