The phrase "and add in a" is correct and usable in written English.
It can be used when you want to include something additional in a list or a process.
Example: "Please review the document and add in a summary at the end."
Alternatives: "and include a" or "and insert a".
Remove from the heat and add in a half teaspoon of freshly ground black pepper.
We also had to slow down our process and add in a new step of the radio interviews, acknowledging that design is an 'emergent' process.
Finely chop a load of cherry tomatoes and shallots and add in a bit of white wine vinegar, olive oil and loads of fresh coriander.
Microsoft is also set to add new multi-desktop views, to help with multi-tasking, and add in a host of new tools and software for businesses.
(It was Asher's idea to tear off the head of the famous Saatchi & Saatchi poster of the pregnant man and add in a joke about "defacing public property").
We must restart from the proposal for a "European debt redemption fund" made in late 2011 by the council of economic experts to the German chancellor, which was designed to pool all debts exceeding a country's 60% GDP limit, and add in a political component.
If you want to write software for BlackBerry, you take your own text editor, some "ant" scripts they give you, and add in an infinite supply of patience.
Go neutral and add in an eclectic mix of pillows to round out the bohemian aesthetic.
Start with synthesis, accessorize with tasteful co-signs, and add in an element of elusiveness.
I do recommend that you pump out your holding tanks and add in an odor treatment product.
"Just this last indulgence," she writes, and adds in a postscript: "Ask McEban to come with you...
