This is a bug on Windows. The keyword list stops functioning after about 1630 or so keywords. The bug has been logged.
The one workaround we've found is to make the keyword list hierarchical by nesting keyword families together. This will shorten the list and allow more keywords to be viewed and/or selected and used.
Workaround: using a keyword filter shortens the list and allows the selection.
This reply was created from a merged topic originally titled
Lightroom LR3, LR4, LR4.1RC2: long keyword list looses focus.
Collapsing the hierarchy in the column isn't always a viable workaround. The only way in LR to reliably find photos explicitly assigned with a parent keyword is to use Flat View in the Keyword column.
Why has selecting a keyword with a mouse click in Lightroom5 suddenly stopped working?.
I have been working with Lightroom5.3. My list of keywords had gotten long so I experimented with adding hierarchy. I seemed to work as advertised with dragging other keywords under the parent keyword.
I left to do some other tasks. When I resumed I could no longer highlight (or select) a keyword in the list of all the keywords, let alone drag it.
I am using Windows 8.
I don't agree with LR team's priorities (or maybe it's marketing priorites) - I think bugs from 4 years ago should be fixed before adding new features like the ones in LR CC.
I was looking for a keyword I couldn't recall. When I checked the Keyword list in the right side panel I noticed that the list stops at the work Oak.
I tried the Library Filter and it displays a little further, up to the phrase "OK Corral".
I know there are many other keywords.
I have a total of 4,838 keywords according to the Library Filter
Total of 160,000 images in the catalog.
Windows 10 Desktop PC
Sure hope Adobe can fix this some day.
As IT pro I got curious and dug into the SQLite DB (which is the catalog). I found some redundancy in the tables and something that worries me: the ids for all keywords along a path down hierarchy to any keyword are stored with this keyword as a string. This could be a potential issue with deeply nested hierarchies.
Currently I am at 2157 keywords on my list with 1841 being on the top-level. Bit by bit I manage to get more structure into it and bring LR back to life. Not really happy.