The phrase "working on modifying" is correct and usable in written English.
You can use it when discussing efforts to change or improve something, such as a project, document, or system.
Example: "I am currently working on modifying the software to enhance its performance."
Alternatives: "attempting to adjust" or "engaged in altering".
We have been working on modifying the CTSiM interface and adding tools to help alleviate some of the students' challenges that we have identified in this paper.
Also, we are currently working on modifying the software in ways that avoid loading genotypes in in memory.
The WOMBAT Collaboration is currently working on modifying the NICS Barrier Tool to create a trial recruitment tool.
We are currently working on modifying PAVE so that it can use the results of various assemblies to take advantage of these custom assemblers and integrate the results with the PAVE mate-pair assemblies of Sanger reads.
"Older women taking antidepressants, like everyone else, should also work on modifying their other risk factors for cardiovascular disease, such as maintaining a healthy weight and controlling cholesterol levels and blood pressure".
Other groups have worked on modifying the surface chemistry of lignin to reduce its affinity toward enzymes.
After the war she worked on modified versions of the fan for use by workers in mines and sewers.
Dr. Rupert Fray of the University of Nottingham in England is working on genetically modifying plants so they reproduce the autoinducers.
He and his team are working on genetically modifying haemoglobin to make it less toxic, and then wrapping it in a special long-life plastic cocoon.
Researchers are working on genetically modifying apples to be resistant to bacteria, potentially saving farmers tens of millions each year, and making them significantly cheaper for consumers--the apples would be otherwise unchanged, the same as average apples.
Intrexon has also acquired the company that developed a recently approved genetically modified apple resistant to browning and a British company working on genetically modified insects, such as mosquitoes that might be tested in the Florida Keys as a way to prevent dengue fever.
