Use pub.string:substring and set beginIndex =13 and endIndex =14.
Then add a branch then paste the /value in the Switch property.
After that add Sequences below the branch and label each one 0,1,2,…,9.
In the sequence with the label 0 add a pub.string:substring below it and take the first 14 digit then add pub.string:concat to concatenate the value retuen with the { symbol.
What you’re describing as the target format is known as zoned decimal. The PSUtilities package from SAG/wM has a convertStringToZonedDecimal service you can copy. It handles leading signs, negative numbers, padding, stripping the decimal, etc.