बौधायन श्रौतसूत्रम् (कृष्ण यजुर्वेद तैत्तिरीय शाखा - सम्पूर्ण प्रश्न एवं श्रौत-याग कल्प सटीक)

/ ꣳ) or 'ꣳ'?
It has anusvara with crescent underneath: ꣳ (U+08F3 or U+A8E3 Vedic tone candrabindu).
Yes, ꣳ is standard in Devanagari representations of Vedic texts (Gum-kar / Gomukha).

Let's check all line markers:
The prompt asks:
"Prefix each line with line marker like , ."
Wait, should the page header also have line markers, or just the text lines?
Usually, include the header as well, or start from line 1 of the text. Let's make it unambiguous: provide the header, and then line-by-line with to , then footnote separator, then footnote lines.

Let's double check line 4:
"स्त्विष्टिमदृष्ट्वाय '"
Wait, is it connected to line 3?
Line 3 ends: "...कपाला-"
Line 4 begins: "स्त्विष्टिमदृष्ट्वाय '"
Yes, there is a hyphen at the end of line 3: "कपाला-".
And line 10 ends: "तवोति-"
Line 11 begins: "भिरित्येतासां..."
Line 16 ends: "निर्वपेदित्यु॑-"
Line 17 begins: "तयैष्ट्या..."
Line 18 ends: "पश्च