I wouldn't bet on you being right here: Jensen's rights stay with Rangers courtesy of him being an RFA. Like Borgy, Jensen wasn't signed to NHL, so there's really no "transfer" happening under transfer agreement or anything.
Here's a CapFriendly tweet from a couple of years back listing all Group 6 Players at the time. Everyone listed have a cap hit which means every one of them were signed to a NHL SPC at the time. I'm fairly certain that to qualify for Group 6 UFA the player needs to fulfill the criteria (=to be 25 and not have played 80 NHL games) at the time when his free agency begins.
CapFriendly defines Group 6 UFA as player whose contract is
expiring (so, didn't already expire three years ago):
NHL CBA FAQ - CapFriendly - NHL Salary Caps
CapFriendly lists just one guy not currently under SPC to be a Group 6 UFA this year: Nicolas Kerdiles, whose latest SPC ended after season 2018-19 at the age of 25 (and who got his UFA 6 status at that time):
Nicolas Kerdiles - CapFriendly - NHL Salary Caps
Browse - CapFriendly - NHL Salary Caps
Yet there must be any amount of guys who served a three year ELC, didn't much get to sniff the NHL airs and didn't get re-signed to an SPC but went back to Europe or wherever. These guys don't get to return to knock the doors of NHL teams at 25 as Group 6 UFA (but might already have become UFA courtesy of not having been even tendered the QO when their ELC was up; these are the "UFA no QO" guys on the CapFriendly listing that can be found behind the "Browse" link).
Case study: Max Friberg played 5 seasons under NHL contract and 6 NHL games until leaving for SHL after 2016-2017. He was 26 on last July 1st, didn't qualify for UFA, didn't qualify for Group 6 UFA, is currently a RFA for Canadiens until July 1 this year when he qualifies for UFA.
Max Friberg - CapFriendly - NHL Salary Caps
In any case, Panthers don't need to make successive QOs to Borg to retain his rights:
They need only give him the QO, in his case $874,125 (105 percent of his last year base salary $832,000) just once, this year as his SPC expires. If Borgy now chooses to pass that and won't sign a SPC with FLA, FLA will retain his rights until UFA and can negotiate with him for a league minimum SPC if they like.
The standard expiration date for the QO is July 15, 5 p.m. NY time, but the team can extend it if they so choose, and anyway this year for obvious reasons there's bound to be some arrangements for the off season dates, so there's no hurry to get anything done right now.