Keywords in Lightroom - can't see the entire list

Exactly the same problem. Seems to be a rogue keyword that I created once and is no longer in the list and does not export, nor show in tags in Windows 10 explorer. Just shows up when I look at Keywords and Containing Keywords in Lightroom. Seems to be a bug I will just have to live with. There seems to be no way to edit it out in 1st option of Keyword Tags under Keywording.  I can change the keywords on the jpeg photos in Windows explorer and this shows correctly in Lightroom under Enter keywords but not the other options. It looks like the only way to get these keywords off the photos is to start a new catalogue and import the photos. I have not tried this yet but it should work. 
What I have learnt from all this is only apply keywords in a flat list - avoid heirachial keywording as in the end it will give you trouble and is quite unnecessary for most of us anyway.

"because I have probably 1200-1500 stock images already with many keywords, I really don't want to mess those up..."

Dragging those keywords under parent keywords needn't affect how the images are exported.  You can edit the parent keywords and uncheck the option Include On Export, so they won't appear in the exported photos in the industry-standard metadata fields read by the stock agencies.

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"my problem right now is that I can not even add a new parent keyword..."

What happens when you try these steps? 

1. Click "+" in the Keyword List panel to create a new keyword named "XXX":

2. Type "XXX" and the name of another keyword into the Filter Keywords box of the Keyword List panel:

3. Drag the other keyword to XXX.

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Thanks much for the response.

I understand the concept of the hierachy and collapsing down the categories... my problem right now is that I can not even add a new parent keyword...

So building those top level keywords and dragging the existing keywords into groups is not possible... I can't drag and drop...

I did export the list and review them... there are probably plenty I can group...  but because I have probably 1200-1500 stock images already with many keywords, I really don't want to mess those up...  

I guess I could try to break down my catalog into smaller ones as the keywords are associated with the catalog.. build several.. clean them up with the same keywork hierarchy and then merge the catalogs back together....  seems like a pretty drastic measure just to be able to move a keyword around on the list!

Pretty disgusting when you think I'm keywording for "ADOBE STOCK" and their own damn product keeps you from a decent workflow...

I'll keep trying...   erasing might be my last option!

Frustrating!

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"thought I would begin to group them in a hierarchy and assign some synonyms so I don't have so many... but I have to be able to manage the list first."

As described in the links provided by WobertC, there's a couple of tricks to introducing and managing a hierarchy when you have more than 1500 keywords.

1. Keep most of the hierarchy collapsed, so that fewer than 1500 keywords are showing at any one time.

2. Enter one or more search strings in the Keyword List search box, and it will show just those keywords (and their ancestors) containing those strings:

Then you can easily drag and drop keywords to the desired parent keyword without scrolling excessively and without tripping over the 1500-keyword limit.

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"I chatted with tech support.  They said if I installed the latest 9.2 from the 9.1 I was using it would fix the problem... it did not!"

Unfortunately, Adobe tech support will often say anything to close out an issue. 

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cleaning it up in a spreadsheet and reimporting if that is possible...

It is possible BUT it does NOT re-link the keywords to the photos in your catalog, so big problems! Do not do!

This would only work ok when beginning a totally new catalog.

How do I get to remove keywords from a hierarchy AND be able to see all of my keywords.?

I do not think you will be able!

I seems this is a bug that has been reported long ago (8 years? since Lr1?)

See the forum thread at-

https://feedback.photoshop.com/photoshop_family/topics/i_cannot_access_the_whole_keyword_list_to_edit

Create Parent keywords with many child-words. And as you drag a visible KW hovering over a 'Parent' will open up the contained list.

https://lightroomkillertips.com/controlling-keywords/