The Insert Action by Name search knows mostly about words, so you can often use just the first letter. For example “s v t c” will select Set Variable to Calculation.
You can also duplicate or option drag existing actions which may be a quick way.
You can copy actions into Named Clipboards and paste them using macros if desired. You could also use exported action files and drag or import them.
Most fields include type completion, and you can press Escape to immediately trigger the type completion. So for example “Sou[escape][return]” will select the variable Source.
And yes, it remains a deep irony that Keyboard Maestro is itself very challenging to control.
I’d be interested to hear other people’s answers as well, and perhaps any suggestions for future improvements. For the most part I find the design of the macro is typically more time consuming that the time spent making the macro, but other people might have different expierences (I doubt I’m typical ;- ).