When using a certain tool, hold down the following keys to temporarily activate a related tool.

Selection

Any tool except Selection tool

Link/Unlink

Selection tool

Alt + (with a clip selected)

Block move

Block Select

+ Alt

Block copy

Block Select

Alt

Multitrack Select

Track Select

Alt

Multirazor

Razor

Alt

Slide

Slip

Alt

Fade Adjustment tool

Selection

+ Alt + when over a rubberband

Precise pan or volume

Selection

+ drag pan or volume rubberband

Add default transition at cursor (A/B Editing mode only)

Selection

+ Alt + + click transition area