Dear All,
The problem is already solved. A friendly and kind advice (or 'hitopadeśa') from Dr. Viacheslav Zaytsev from the Institute of Oriental Manuscripts of the Russian Academy of Sciences, St. Petersburg.
To whom my special thanks.
In fact a simple operation. To produce, say, ndrya: from the symbols table of, say, Arial Unicode, select न, add virama, add द, add virama, add र, add virama, add य:
[na + virama - n + da - nda + virama - nd + ra - ndra + virama - ndr + ya = ndrya]
न - न् - न्द - न्द् - न्द्र - न्द्र् - न्द्र्य
द्द ष्ट्र ह्म
The same rule goes for santipur OT, bengali fonts, like shonar.ttf or vrinda.ttf, etc.
Best,
Artur Karp
Senior Lecturer in Sanskrit and Pali (ret.)
South Asian Studies Dept.
Oriental Faculty
University of Warsaw