Is there a way to set up a track with audio and then another that will record the effect of scrubbing through the first track (forwards or backwards)? I have tried but nothing records unless you hit the record button but that makes the first track playback and seems to disable the scrub effect.

Tempo envelope? 

Ah yes, go to file/save live output. Uncheck save output only when playing or recording, and maybe also stop saving output on first stop. Scrub away! If you selected stop saving output on first stop (I am not sure if this is necessary) just go back to file/save live output and uncheck it and it will prompt you to stop recording. Will any other daw let you do this?

It also works for (alt jog)looped segments. Hold alt while jogging/scrubbing to loop a section around the play cursor. You can set how long the loop is and whether or not it is in front of and/or behind the play cursor in preferences/playback/looped segment. The default is -88ms (behind the playback cursor) I think.

Maybe it needs something more visual like a right click option on the record knob to record without engaging play. Then it could have a bar to show how much has been recorded and you could use stop to stop. Ideally I would like to be able to record like this into another track too.

I've said for some years (yup, really!) that something like a record-enable button in the master track would be a good way to bring the 'record live output' facility more into the interface.

I do this by having 2 project tabs open, one for recording to and the other to do the scrubbing. 1. Preferences > audio device settings > audio system: WASAPI, mode: shared loopback (CAUTION). 2. Mute track that will be recording, then arm and start recording. 3. Switch to scrubbing source project tab (all tracks here should be disarmed) and perform. 4. Switch back to recording track. Stop, disarm, then unmute to playback. 5. Return audio device settings to normal as soon as you have what you want recorded.

As this has already been necrod.... Birds' global sampler is the answer.