Dotted circle Matra vowel signs in Devanagari

There is a unicode glyph U+25CC = dotted circle

How may we use it to make glyphs?
Some existing Devanagari vowel signs (U+0940) and vowel accents (U+0902) display this,

however when we add a new character and a new glyph,
then how to use U+25CC alongside our new glyph?

We have added the new character vedictonedoublesvaritacomb (U+1CDA)
dottedCircleQuery.jpg

The dotted circle is shown when the shaping engine detects a combining mark is not correctly connected to a base character. For example when such mark is on its own, as you show in your screenshot. I do not know why it fails with vedictonedoublesvaritacomb.

The dotted circle not only fails with vedictonedoublesvaritacomb,
rather it fails with every new glyph we insert using add character.

We added the unicode block Vedic Extensions that wasn’t present earlier, none of the new combining characters displays the dotted circle. ding a new
We also added a new character from Devanagari block, that also fails to display the dotted circle.
dottedCircleQuery2.jpg
Isn’t there any setting to be done when adding a new combining glyph to link it to the dotted circle?

We found the solution. It is working fine in Microsoft Office 2016 and 2019 versions.

It also works in Libre Office Writer version 6.4.6.2 with the Sanskrit language pack.
dottedCircleWorks.jpg

We notice that in the current year 2022, ebooks (ePUB, kindle) have incorporated the Unicode 14.0 specifications for Sanskrit fonts and are now enabled to completely display all glyphs in Unicode blocks - Devanagari, Vedic Extensions, Devanagari Extended.

Question: For Devanagari, there is attachment of mark to base. If an incorrect mark is typed, the dotted circle gets inserted. Is there a way to override this dotted circle ONLY for a few specific glyphs? The reason we ask is because even though all Devanagari glyphs are now correctly displayed, the shaping engine hasn’t been updated to account for all these new symbols.

PS: We find that if we do not insert the dotted circle $01CF in our font, then for new symbols the marks get attached, however then it significantly increases the chance of spelling mistakes.

I am not sure if you mean override in the preview of FontCreator or in other shaping engines?

I don’t think you can override in other shaping engines.

I am not sure if you mean override in the preview of FontCreator or in other shaping engines?

Oh! Ok, Thank You.

Question: Could you please tell us if there is a way to insert a break point in OpenType designer of the preview of FontCreator so that we may see how exactly the AboveBase mark attachments or positioning or ligature substitutions are happening, so that we may correct our code?

Use the proofing tool for this, see:
Font Proofing – OpenType Layout Features Unleashed

Proofing Tool is excellent. Thank You.