First I am running  SW 2014 SP5

In a part file (SLDPRT) I have set the following:

Good works fine.

Pops up thusly in the Property Tab Builder:

The tab builder design is thus:

With a “text file” called “drawing_#.txt” to pull or select items from:

So that I may pick if I desire say:

Which makes this happen:

OK

Back to:

After editing a field in the Property Tab Builder dialog user input box, say in “title line 1” or any other field that needs editing and
one applies changes with the value as shown above:

One gets this in:

The Custom Prop is no longer tied to the “SW-File Name”

Question how do I get the Custom Prop to stay tied to the “SW-File Name”?

It is as if it obtains the “Evaluated Value” and returns this “Evaluated Value” to the “Value / Text Expression” field upon apply.