Allow parameters to define lengths of substrings

[simoncriswell]

Is your feature request related to a problem? Please describe.
I am creating many tags with names on them. The file name has the entire name, First Last, and I have one text box for First and a second for Last. I want a way to easily adjust the length of each text box.

Describe the solution you'd like

1. I am using the expression {_.component[0:5]} to grab the first name. I want to be able to replace the 5 with a Name_Length parameter that I can update separately.
2. The second ask would be to implement a search function somehow to find the index of a certain character in the string. Not that familiar with scripting, so this might be something I could do with that.