I think the Neale Hanvey situation possibly gives an idea how that might be handled.
The SNP suspended him & withdrew support & funding. But they couldn't remove SNP from the ballot paper as it was too late when the issue kicked off.
I don't know that anyone would jump after the deposits/names have been registered for each constituency/list but before the election as they'd leave themselves wide open to being left high & dry. Might not be ethical but I think anyone on constituency ballots will sit tight and make a move after the election is over. They'd get absolute pelters for it! But I think they'd either need to give up their constituency seat now, and have no chance of getting a seat, or make a decision much later.
It does highlight the difficult position the SNP are now in, mainly because they stuck with Sturgeon who is making all the bad decisions that are pushing people to leave.
That 'off the cuff' video that she posted over a handful of misogynist student tantrums, given all the women who have now left (including a Glasgow councillor today who was heavily involved in the equal pay case for women), really does look so much worse in hindsight than it did at the time (and it was awful then too).
Her judgement is seriously off & i find her take on this situation seriously bizarre.