OK. There may be a simpler way to do this, but here is something I have tried. It's tricky because if you want to convert ALL numbers, you still need to preserve some arabic numbers within markers and chapter and verse numbers (which will be handled by PA).
In changes.txt, add the following lines:
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# An @ sign will be used to identify numbers which should not be converted.
# These expressions find chapter numbers and verse numbers, and places an @ symbol after each number.
"(\\[cv] \d)(\d)(\d)(?=\s)" > "\1@\2@\3@"
"(\\[cv] \d)(\d)(?=\s)" > "\1@\2@"
"(\\[cv] \d)(?=\s)" > "\1@"
# Verse ranges
"(\\v (?:\d@)+-\d)(\d)(\d)" > "\1@\2@\3@"
"(\\v (?:\d@)+-\d)(\d)" > "\1@\2@"
"(\\v (?:\d@)+-\d)" > "\1@"
# Place an @ symbol after each number within USFM numbered markers.
"(\r?\n\\[^\d \r\n]+\d)([ \r\n])" > "\1@\2"
# These expressions find numbers which are not followed by an @ symbol, and converts them to Tibetan numbers.
in "\d+(?!@)": "0" > "\u0F20"
in "\d+(?!@)": "1" > "\u0F21"
in "\d+(?!@)": "2" > "\u0F22"
in "\d+(?!@)": "3" > "\u0F23"
in "\d+(?!@)": "4" > "\u0F24"
in "\d+(?!@)": "5" > "\u0F25"
in "\d+(?!@)": "6" > "\u0F26"
in "\d+(?!@)": "7" > "\u0F27"
in "\d+(?!@)": "8" > "\u0F28"
in "\d+(?!@)": "9" > "\u0F29"
# Now, get rid of the @ symbols.
"@" > ""
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