You cannot constrain elements to the dynamic Extension Line of a View Title. You also cannot control the properties of the View Title with Instance Parameters. So, you can recreate the Extension Line within the Family and create Type Parameters to control the length This means that you will have to create a separate Type for every length you wish to have. (We typically employ three "Short", "Standard", and "Wide")
If you have elements that you show on the end of that extension line (i.e. North Arrow), then use a Reference Line to control the overall distance of that line. Then, you can Group the extraneous elements with that Reference Line so that they will move along with it.
Corey D. ────────────────────────────────────────────────────────────────────── ⁞|⁞ Please use .Accept as Solution and Give Kudos as appropriate to further enhance these forums. Thank you!