We use google sheet where I post Caller link when I decide. They have to monitor this google sheet and when they are scheduled I update their link. Its a workaround, but it works. I posted similar request as yours a while ago.

grega

On the contrary I believe this only reveals a lack of information and organization on your side.
I use exactly the same workflow all the time since vMixCall was released 3 or 4 years ago, I never faced such an issue with several hundreds of guests. Why? Because I provide my remote guests a very clear and detailed schedule prior to the event which indicates a time slot they are allowed to connect. It also indicates in "bold" the problem they will cause if they don't respect this schedule. Furthermore, this situation is explained during the mandatory test that is done prior to the D day.
That's what producing is all about ! It's not only handling the technical aspects, it's also about organizing and communicating the right information and rules.

I believe the impression and professionalism you show to the guests prior to the D day prevents them from being disrespectful.

I agree there are situations when things must be handled differently, especially when the event is badly organized (on the client side). For example sometimes the event schedule doesn't follow our recommandation to let 30 minutes free between sessions (so that we can connect guests comfortably). In this case we have 2 solutions :
1 . use 2 vMix in parallel. vMix 1 produces session 1 and at the same time vMix 2 takes guests for session 2. In general for such a workflow a third vMix is used to stream and record (using NDI feeds from vMix 1 and 2). Obviously it's more expensive for the client (3 vMix, 2 TD and more pre-production) but this brings a safe solution. And bad decisions have a cost. If the client want it as cheap as possible, they listen to us. Otherwise they pay for their decisions consequences.
2 . when the time slot is too short (like only 10 or 15 minutes), I use a PA (Production Assistant) which texts vMixCalls passwords to the guests on my command at the last minute. They are supposed to be standing by and connect as soon as they get the code. Again we know this in advance, so guests are briefed very clearly about this situation and it works.

Regarding those guests who think they can do whatever they want like staying at work when it's been explained they have to be at home, I have a clause in my contract with the client that says that I reserve the right not to accept this guest if he puts the whole production in jeopardy by not respecting the conditions that were defined. All my clients understand this. All the guests know this clause.
Obviously I have faced this situation. In general we give it a try anyway. If it works at once, OK. Otherwise bye bye... Again it's just a matter of organization and professionalism. All tests are logged and a report is sent to my client indicating where talents are supposed to connect from (as well as connection types (fiber, dsl, 4G), computer brand (mac/pc), browser, and so on). Based on these information I give my opinion if the conditions are perfect, good, medium or bad (image and sound quality). Based on these information the client can decide what to do. Nobody wants to be ridiculous on the D day. SO sometimes they insist a guest moves to a different location or find better equipments. Sometimes they decide not to have a guest join at all. It's nobody's interest to produce crap. We're not in for the fun. We're in because we are pros...
You might think this clause is too much but think what happens in a physical event when a guest comes in late or comes in drunk.

Lastly I can say that the "append" method axplained above also works. It's possible to define sets of vMixCalls and load them in a project. I don't use this but it works.

streaming---pro's Feature Request is https://forums.vmix.com/...o-allow-better-Show-Prep (where I have a +1)

With one exception I agree with DWAM's comments above (in the current topic). The exception has to do with human behavior. We increasingly find that our customers and callers tend to become slightly unprofessional, or rather stressed (perhaps by corona, lack of time, new work habits, etc.). So they do not read, and/or forget, our instructions.

One example, we recenly had a live situation where a minister from the Swedish Government was on a vMix Call and had problems with the microphone. One of the minister's assistants (located elsewhere) had the password and decided to try connecting with her/his computer, which kicked the minister out. And a minute after that another assistant tried from his/her computer - kicking the first assistant out.

I do not see any reason why an "Accept call" function in a vMix Call input would cause any damage, or not being backwards compatible (default Accept call=on). The point is that it would definitely provide better safety measures for us that need it.