As a general rule, as long as you're allowed to continue to descend to the original altitude, being pulled off the arrival isn't a big deal as long as you pop it into FPA and keep descending at roughly the same rate you were at before the vector.
Then once you're back on, making a fix a hard altitude and doing a vertical direct gets you right back where you were.
It also tells you how screwed you are, because our box will tell us what the angle is on the vertical direct. You'll know right away if you won't be able to stay on the arrival.
"Depends".
On the airbus, we have (technically) two managed descent modes, which are both "managed".
Here's the split. Once you start down a managed (VNAV) descent path, the airplane will start descending, join the desired vertical path and then assume that once you reach your path, that you will be in a constant descent to all other fixes on the profile as it planned.
Once you get off the lateral path, the aircraft will still presume you're going to continue descending, even though you've had a mode reversion to VS or "open" (same as FLCH).
So when you're back on path, the 'technique' is to re-cruise by re-inserting your cost-index or re-inserting some of the data on your approach flight phase page on your MCDU because until you do that, where the aircraft is still convinced you're descending as it planned previous to your departure from the managed (VNAV) path, even though you've been droning around in a different mode.
The distinction between geometric managed descent and a profile (I think that's what it's called, I'm having a brain fart, save me
@PeanuckleCRJ) descent mixed in with a new runway and a new restriction is one of our leading causes of unstabilized approaches in the Airbus.
Things that aren't a problem for the Airbus are big problems in Boeings. Things that aren't a problem in Boeings are a big problem in Airbus. Mix in another few fleet types into an ATC environment that presupposes that all turboprops are Brasilias and all jets have the characteristics of mad dogs and CRJ's, we've got a recipe for hilarity.
Every time I'm arriving in SLC with a new pilot, I start the brief early, talk about the various ways they're going to attempt to bone us and with almost 100% certainty, they will (which is great because it's pre-briefed and we've talked about some mitigation techniques) or make up something completely new and unexpected when the inevitable "ZOOOOOOMG! Uhhh, here's a Gordian Knot, untie it! Contact tower on…"