Feature request: Simulator - Enable a way to hold down a button

[martinwork]

Arising from support ticket https://support.microbit.org/helpdesk/tickets/91351 (private)

Is your feature request related to a problem? Please describe.

For example, unable to use the simulator to test a program that requires a logo + A combination

See earlier example and discussion in microsoft/pxt#2408

Describe the solution you'd like

Keyboard shortcut?
Context menu?
Optional panel above simulator?