When using Keyboard Focus mode, (and Keyboard Focus mode will increase your speed, so you should use it), when you want to separate a clip at the cursor position, type b. That’s it. Just b. The mnemonic to remember is break. You can also select an area in a clip with the selector tool and press the delete key, or type command-x, or you can split the clip using command-shift-e (the mnemonic is e, as in the last letter of separate.)
There are additional editing commands which become available if you have enabled Keyboard focus. Typing the letter a will split a clip at the cursor position, and delete the portion to the left of the cursor position. Typing s will split the clip at the cursor position, and delete the portion to the right of the cursor. These can be incredible time-savers. They are useful in almost every editing task I can think of.