I have two equal length walls that intersect, how do I define a bend for only a portion of the intersection length?

We received this STEP file from a supplier (unsure of the CAD system they used to create it).

I suspect they modeled the shape of the whole enclosure as a surface and then used some "recognize" features to turn it into sheetmetal compatible geometry with bends and splits.

We're curious how to limit the bend to a specific length along an intersection like shown in the screenshot below.

How would you define a bend to only be a specific length along an intersection? (Perhaps in order to be compatible with available brake press die lengths)