from io import StringIO
import re

reader = StringIO("""{
    "Bounds": [
        {
            "HasClip": true,
            "Lang": "no",
            "Page": 0,
            "Path": "//Document/Sect[2]/Aside/P",
            "Text": "Potsdam, den 9. Juni 2021 ",
            "TextSize": 12.0
        }
    ],
    
},
{
    "Bounds": [
        {
            "HasClip": true,
            "Lang": "de",
            "Page": 0,
            "Path": "//Document/Sect[3]/P[4]",
            "Text": "this is some text ",
            "TextSize": 9.0,
        }
    ],
}""")


text = reader.read()
pattern = r'"Path": "(.*?)"'
replacement = '"Path": "\\1/1A"'
text = re.sub(pattern, replacement, text)

print(text)