Can I start an H1B transfer while traveling abroad for visa stamping with my current employer?

The question

I’m currently working in the U.S. on H1B with Employer A and have an approved I-797. My H1B visa stamping appointment with Employer A is on Nov 28 in my home country. I just got an offer from Employer B, who wants to file my H1B transfer. Can Employer B file the H1B transfer petition while I’m outside the U.S. for visa stamping with Employer A? Will this cause any issues with the transfer petition, visa stamping, or re-entry? Or should I wait to return to the U.S. after my stamping before starting the transfer process? Thanks in advance for your advice!