You can bail on them but it’s a bit fidgety to do so.
I got a bunch of nav data from a terminal at one of my bases and exchanged em for settlement data at the space station map guy at a rate of 5 to 1
I went to a separate system and landed on the planet I wanted the settlement on. had to mess about with selected missions a good bit to get it to work.
I put it on to new beginnings primary mission and took it off the settlers secondary mission and flicked between a few other secondaries. Then hit the settlement map chart to find a settlement.
Took a few goes messing with missions to get it to work though.
Edit: yeah 1 settlement at a time is the limit… You’ll see a message saying you’ll lose your previous one