This was driving me a bit nuts, so I thought I'd share in case it might help others as an example.
We are using Jira with Structure/Structure.Gantt.
There is a custom controlled field that represents our internal company projects that follows this pattern:
I simply wanted to display the project name/string without the numbers as a column (or grouping) in my structure.
Using the docs from ALM's site, I landed on the combination of REPLACE_AT and SEARCH.
REPLACE_AT allows me to remove the characters from the delimiter (:), but since the delimiter position was variable, I was able to use SEARCH to identify it's location.
I really wanted to define the SEARCH portion as a separate variable utilizing WITH, but I couldn't quite get that working.
If there is a more efficient way or suggestions on WITH, please share!