(Click to enlarge)

Screenshot added to this report. Tried editing again and got a 2nd root when saving. One says 'Go upwards to Root' the other 'Go to this as a virtual root'. None of my entries showing on either.

Okay, forgot this was a fresh install again and I hadn't turned caching off. They are listed now. Not sure how the category called 'Root' got created by saving the original catalogue, or why it's not using the actual catalogue title which is Performers.

Also, when not displayed as a tree, there is still the issue of no link to the parent catalogue.

When trying to edit and rename the Root category that was somehow created, I get the error below:-

Unfortunately a query has failed [UPDATE cms10_catalogue_categories SET cc_move_days_lower=NULL, cc_move_days_higher=NULL, cc_move_target=NULL, cc_order=4, cc_parent_id=8, cc_title='Rock', cc_description='', cc_description__text_parsed='return unserialize(\"a:5:{i:0;a:0:{}i:1;a:0:{}i:2;s:10:\\\":container\\\";i:3;N;i:4;a:0:{}}\");\n', cc_description__source_user=2, cc_add_date=1460930640.0000000000 WHERE (id=7) LIMIT 1] [Column 'cc_move_days_lower' cannot be null] (version: 10 RC5, PHP version: 5.6.20, URL: /cms/cms/index.php?page=cms-catalogues&type=__edit_category&id=7&catalogue_name=performers&uploading=1&keep_fatalistic=1)

Okay, there's a lot to unpick here.

(A) Missing breadcrumb link back to the catalogue

I've added a documentation tracker issue that gives a quick overview of how it's set up. No bug here as far as I'm aware.
http://compo.sr/tracker/view.php?id=2425

(B) "but it was called Root and not the title from the catalogue itself"

This sounds normal. Possibly a little inconsistent, as we give the default catalogues, and new catalogues, the same title for the root category as the title of the catalogue.
However, for a retroactive change we just use the language string 'ROOT'.

We'll fix the inconsistency.

(C) "Found myself on the catalogue category page ... There are no links to the entries I added on that page."

Right, but I think you'd see category links under the root category, so you could get back into the category you'd put them in. This worked when I just tested.

(D) "Tried editing again and got a 2nd root when saving"

There's not a lot of magic here. The root category is a category like another. When you make a non-tree catalogue a tree one, it creates a new category for the root, then moves everything else underneath it.
I think this is what is confusing you, I think possibly you weren't considering the root category an actual category.

I think we could be smarter. If there's only one category in the catalogue, we could just make that the root. I'll add a new tracker issue for that. But it's a minor thing really.

http://compo.sr/tracker/view.php?id=2426

(E) "and I hadn't turned caching off"

There certainly shouldn't be a caching issue, as when you edit a catalogue it flushes the relevant block caches.
I just checked and we're not flushing out the main_cc_embed block when a catalogue category is edited, and we should - which I'll fix. But I doubt it is related to this, as you were editing the catalogue not a category within it.

(F) "When trying to edit and rename the Root category that was somehow created, I get the error below:-"

This was a bug, fixed.