When editing yaml in automation / ui / …, if you type “switch.” or “light.” you get the list of entities.
When tabbing, the first entity should be autocompleted, but now it only indents the line one step further.
Hit the down arrow once, then hit enter.
That’s a way to do it but any text editor for yaml or anything else use single tab to autocomplete.
I think this is not ergonomic nor intuitive at all
Most tools I use follow the same protocol with dropdown menus. 