how do i select all in transfer tab?

press ctrl c in the transfers window.

CTRL+A not C.

CTRL+A = select all
CTRL+C = copy
CTRL+V = paste
CTRL+X = cit

These are common programm shortcuts.
Multi-selection:
CTRL+Mouse Click = De/Select one more
SHIFT+Mouse Click = De/Select all elements in the list between last clicked element and current one