I would like to use CLion (or VS Code), but both of them fail to properly provide Qt/QML related docs (component and types and properties help).
I can start Qt Assistant next to IDE and go there. Yet, I failed to ensure ONLY one instance is running - partial solution can be done with external script which kill already running instance and start new one.
Secondly - I miss option to open Assistant on given keyword like 

--search-keyword Rectangle