Way around 300 character limit on ProcessFlow string variables?

Use MessageBuilder node instead, only thing is if you have any UserAction nodes, the value is lost when it stops and waits for user to take action because MessageBuilder values are stored in memory and not in the LOGAN tables.

If you need the information to last after a user action you could save your information to a TEXT file with the workunit number as the file name and then at the end of the flow delete the file.

(Also, as a note on using Message Builder - this is a great node but make sure you empty the value if you go through a process more than once in a flow.)