Double-click mask with Selection tool or select mask in Timeline panel and press Ctrl+T: Enter free-transform mask editing mode

Ctrl+drag, then release Ctrl while dragging: Set brush hardness for a paint tool

Select Path property in Timeline panel and press Ctrl+T: Enter free-transform path editing mode

Source: Adobe

(Note: Also goes to beginning, end, or base frame of Roto Brush span if viewing Roto Brush in Layer panel.)

Note: To momentarily activate a tool with a single-letter keyboard shortcut, hold down the key; release the key to return to the previously active tool. To activate a tool and keep it active, press the key and immediately release it.