[Hey Jude]

Growing these for the first time - should I pinch them out? Many thanks, Jude.

[arugula]

I would just leave them to get on with it. If you are concerned about them getting droopy, this is what they do, have a look at Google images.

[Yorkie]

Totally agree.  They do branch of their own volition.  (And self-seed prolifically though are very easy to get out!)

[Hey Jude]

Thanks to you both!