(edit) v1.21+ has some clipboard features in the Advanced menu
I'll give it a shot

> This addon is great but is it possible to run all search engines in folder at the same time?

When using the popup menu, yeah ( context menu folders have no usable click events ). Clicking the middle mouse button on a folder will search all engines in the folder with the current search terms and send the results to background pages. You can change this behavior in Options -> Quick Menu -> Search Actions -> Folders column.

> 2nd thing is hotkey assigned to search engine. Is it possible to make not a single letter but e.g. 2-letter / 3-letter phrase?

Not currently. Be aware, the hotkeys only work with the quick menu opened. If you're looking to select text and press a key to immediately perform a search, you might want to open the qm using the keyboard method ( using CTRL for instance ) and then you can press your preferred search engine hotkey to execute a search. If you're looking for more functionality, consider opening a thread on the github support site.