Hello again, Andrew :-)!
If you've got maneuvering and general boatmanship well under control, you've obviously got the battle won already!
Giving you specific advice
on where to find the "good spots" is clearly more than we can do in this forum - Europe's inland waterways being extensive, as you say yourself.
What I would do, is simply google
for names that strike your fancy. This one came right up when I googled "Kiel Canal":
The Kiel Canal
Chase the leads contained in it and you will find many interesting things! The Kiel Canal was built, as I'm sure you know, to enable the ships of Kaiser Wilhelm's navy
to transit from the naval base of Wilhelmshafen on the shores of the Northsea across the Schleswig-Holstein isthmus to the port of Kiel on the Baltic
in furtherance of the kaiser's ambitions for WWI. You will see that there are may facilities for a little boat such as yours, and walking from the canal to the nearest Kaufmann
to replenish your vittles is perfectly possible in many places, as is having a tipple at a Gasthaus
You can, from Brunsbüttel, go up the River Elbe to the stunningly impressive port and city of Hamburg. You can, from Kiel, enter the waters the Danes call the "South Seas", the waters to the south of my native island of Funen, to the south of which you will find little islands of immeasurable natural and architectural charm inhabited by cheerful people who know nothing better than introducing foreigners to what in their minds is very heaven!
Distances are small, and in the summer the weather
is utterly benign.
If you wish to go the other way, transit the canals until you enter the River Rhine. From there you can enter the Danube, and you know where THAT will get you :-)!
But before you do that, make sure you read, if you haven't already, Erskine's Riddle of the Sands
which is set in the Wattenmeer and the islands off the mouth of the Elbe. The story is wonderful, and you might spend a year or two exploring just exactly what lay behind the story :-)!
As I said, there is far more to tell than we could possibly cover in this forum, so here is a suggestion for you: Why don't you spend the rest of your life developing a "Cruising Guide to the Waterways of Europe"? As a model to get you on the right track, have a look at Waggonner's Cruising Guide
that is the standard reference work
in these 'ere waters?