Tool Modifier list (eg brush + alt-right click)

Is there a list of tool modifiers? For example, when using the brush tool, alt-right click changes the cursor to a preview of the brush size that you change by sliding left or right. A great feature! But I don't know where I learned about it.  It leaves me wondering what other tool modifiers are available.  There is a great list of keyboard shortcuts.  But I haven't found a list of tool modifiers.  That is,  a list of tools that shows what modifiers are available for each tool.