Substituting white flour for maida in making Indian samosas

There has been quite a bit of confusion here concerning maida (which can be labeled all-purpose, especially in India). The top answer on the question that you linked to was actually incorrect. It has been fixed. Maida is actually a very low protein flour, much like what would be called cake flour in the US. I suspect and would appreciate if you can confirm that your use of the term "all-purpose flour" stems from the Indian use of the term, not that your recipes call for what Americans would call "all-purpose flour".

In answer to your question, yes, you can substitute what you know as white flour and what I know as all-purpose flour (`10.5% protein) for maida by replacing some of the white flour with cornstarch or potato starch. The best reference I could could find for the percentage of protein in maida was The Fresh Loaf, they say that, on average, maida contains 7.5% protein. To get from 10.5% protein to 7.5% protein, you would need to "lose" 3 grams of protein per every 100 grams of flour. By replacing 28.6 grams of white flour with potato starch or cornstarch, your mixture would have the the 7.5% protein content of maida. That looks good on paper, but my gut says to split the difference. I'd first try a mixture of 15 grams of potato or corn starch and 85 grams of white flour as a substitute for 100 grams of maida. The use of cornstarch in that way is commonly done in the US with our all purpose flour to emulate our low protein cake flour. cake flour with corn starch

In case the international flour terms aren't complicated enough, I understand that in Israel what is generally called cake flour has added leavening agents, it's like what I would call self-rising flour. Confused yet? I'll repeat here what I said in comments above:

"It's confusing. In India (and therefore also on its exports) maida is sometimes labeled "all-purpose", but it is more like what Americans call cake flour. Israel has its all-purpose, which is less processed than the all-purpose in the US. What is called cake flour in Isreal would be called self-rising flour in the US. What Isreal has that is the closest to what Americans call all-purpose is called white flour."