It sounds like digiKam has similar features to the Organizer at least in terms of keyword structures.
In the Organizer, a keyword can be either a keyword category/subcategory to which you can then add keyword tags or another subcategory or a keyword tag to which you cannot add subcategories. Keyword categories/subcategories have little arrows next to them to expand the category.
Within a keyword category the keyword tags are automatically displayed in alphabetical order followed by any subcategories also automatically displayed in alphabetical order.
But in any case, you can then click and hold any keyword tag or category/subcategory and drag it to wherever you like in the keywords tree structure. For example, I have a PRINT keyword tag which I tag images files that are ready for printing after being set up with soft-proofing. I have placed that PRINT keyword tag at the top of my keywords panel.
Used diligently and plentifully, Keyword Tags are a very quick means of finding just exactly the image(s) one is seeking.
digiKam and many other programs also use colored flags, and not just a single flag, but from one to five flags of the chosen color; plus, along with the standard one to five star rating, they will allow many different colors of stars.
Too much such information could get overwhelming; but, if one has a good memory and a sensible approach to all of this, having so many different means of keywording, flagging, starring, and then simple tagged or not tagged, one can for certain separate the sheep from the goats.
Yes, totally agree and I do pretty much the same, but just using a different tool.
Photoshop Elements 2020 (including Organizer), Elements+, Premiere Elements 2021, Topaz - Denoise AI, Sharpen AI, Gigapixel AI.