Windows has just blocked me from running trusty old Kombilo 7. I tried downloading Kombilo 8 but both Windows Defender and Norton prevent me from installing it.

I therefore tried the latest Drago, which seemed to install OK, and I successfully created a small database. But when I tried Pattern Search all I got was the window below. The peripheral controls are responsive but I see no board on which to input the position, nor can I find anything helpful in Help or Options. It occurs to me that, as the position search function is borrowed from Kombilo, perhaps Kombilo needs to be installed, too, though I'd find that (a) amazing and (b) totally unhelpful. I do see a board when using the normal game-replay and other functions.

Any suggestions, please?

You have to have a separate game window open as well (either by loading a SGF, or by creating a new board and populate it manually with the position you want to search for).
In the game window, you select a search area by right-click and drag - it will be highlight in red.

You also need to have a database window open (Database | Open database) - you may have this open already if you just created a new database. (This is useful to know if you have several databases - the Search is contextual to the one you last open and selected).

Then you click "Search" in the search window (the one you showed a screenshot of). If it finds some match, the Search window will show "x games found in xyz.db" at the bottom, where xyz.db is the name of the file you saved your game collection as. The Search window is "floating" on top of the application.

Then you go to the window with the game collection, which after a successful search has the list of matches. From the View menu you can make the matches show as "Preview game information" (useful if you want to sort by game date for instance) or "Preview board thumbnails" (the default). You can select each match and it will show it in the same database window, and use the "<<" or ">>" (from the menu bar) to easily navigate back and forth through the matches.

Thank you, Sorin - a model of clarity and efficient explanation!

Drago is certainly not intuitive, but it seems packed with features so I suppose there has to be a trade-off there.