The phrase "allowed to add a" is correct and usable in written English.
It can be used when discussing permissions or conditions under which something can be included or incorporated.
Example: "In this project, you are allowed to add a new feature if it enhances user experience."
Alternatives: "permitted to include a" or "authorized to insert a".
At the same time, existing large banks were allowed to add a wide range of commodities-related activities.
The Clarks were allowed to add a 300-square-foot addition for a new kitchen to the reconstructed house.
After several weeks of intensive physiotherapy I was allowed to add a gentle stroll to my day.
The facade could not be altered, and developers were not allowed to add a roof terrace because it would have involved drilling into the roof, Mr. Hinder said.
In future, councils will be freed to cut business rates to attract new jobs, and elected mayors in big cities like London, Manchester and Sheffield will be allowed to add a premium to rates to pay for major infrastructure projects.
However, after discussion with the cathedral authorities, Ashdown-Hill was not allowed to add a relic of the True Cross, and a relic of St Francis which he wanted to keep Richard company.
Beginning in 1980 the eligibility year for nominations was set to the calendar year, rather than December November as initially conceived, and the SFWA organizing panel was allowed to add an additional work.
The patients were allowed to add an additional agent after 6 weeks.
During interbreeding, small mutations are allowed to add an element of randomness, and in this way aid the genetic algorithm in finding the optimal solution.
This allows to add a new replicated server only when the active ones are in maximum CPU frequency and become overloaded.
There's also an FM radio, photo album, ebook reader, and an expansion slot that'll allow to add a 4GB SD card.
