NO, IT CAN NOT.
The Plantronics 2.5mm 6in. Quick Disconnect Cord (catalog # 1230 on website) looks like it would work for Leitner folks that need a shorter 2.5mm cord... but it won’t.
It’s specially designed for the Plantronics CA10 and CS10 system. SO unless you have one of those very specific systems (which most people don’t) this will not work for cordless phones and 2.5mm desk phone headset jacks. You will only get one-way sound, at best.
We currently do NOT have a shorter alternative to the Leitner 2.5mm cord in all of its 8 feet of glory.