Unsure about the first - it is possible that you are adding an empty force and then attempting to add subordinates to it - this does(did?) crash the Estab editor.
Ensure that you:
Create the supreme force - and immediately open the unit's details, select the Estabs list and drag something to the unit.
Now you can add a saved force list, or create a force by hand - but in the latter case, do always ensure that you fill a unit's Estab type before adding any subordinates, or before attempting to run it.
I hope that is all the issue is, but if you confirm that you are doing that and the problem persists then some more details might help pin down what is going on.
In fact, I have only two units in my estab, just for running some tests
As soon as I want to create a Supreme Force (Inser), it crashes, so I can't create any.
I think it needs a minimum number and type of elements in order to be valid - at least HQ, Line and Base (one of each) as far as I can tell.
And this is for each side, so you'd need to add ~4 more elements to make a working file.
By far the easiest method to work with is to add/modify a copy of an existing file, as everything should be set and working, and troubleshooting is easier... it is possible to do though, and I have built a small test estab from scratch. Not that it is 'wrong' to start with a clean slate, just saying that is the easier route for the first tests.
I've got three sides (one for test, not used), each containing three forces in one service. Those forces have at least one vehicle.
But now the game crashes as soon as I create a new scenario, after the choice of estab and map
Within your two sides you may have several nationalities, each of which may have more than one service if required.
For each side (though not each service) you must have a high level HQ (for the supreme force), plus (AFAIK) a field HQ, line unit, base - the support units are optional, but as a realistic Estab would require some, I'd add something - probably the easiest is to implement a Regt structure with a single type of Bn and Coy.
There are also some requirements for filling in the force/service/nationality/side data that are important but not well documented. I think for example that you must use an image for the various 'flags' - that although it is possible to tick 'no image' this is not valid.
I'd be happy to look over what you have - but I'm afraid that guessing sight-unseen is going to take a while on something as complex as building a new Estab from scratch...
